If, as many people at CBS News expect, John Roberts eventually succeeds Dan Rather as the network's star anchor, he undoubtedly looks the part.

Impossibly handsome. Thick head of hair. Deep baritone voice. Brimming with self-confidence. But appearances to the contrary, he's not just an anchorhunk mass-produced by Central Casting.

Roberts is, among other things, a former rock-and-roll radio deejay in his native Canada, spinning records by Led Zeppelin and the Bee Gees. He hosted a TV show called "The New Music." And, he says, he doesn't lust for the limelight.

"I don't want to be a star," Roberts says with typical earnestness. "I've never seen myself that way. I don't see myself as the type of person who could be an effective star. I'm a regular sort of person and I don't aspire to stardom. I don't want the trappings of it, the mantle of it."

Like it or not, the 43-year-old journalist is heading in that direction. He already anchors the Sunday edition of the "CBS Evening News" and regularly fills in for Rather. He sat in for Rather the last week of April and, one day, also filled in for Bryant Gumbel on the "Early Show." His day job, since last fall, has been White House correspondent, a key ticket-punch in television's cinematic sweepstakes.

"Because he's very attractive, it would have been easy to typecast him as a pretty boy with a nice voice," says CBS News President Andrew Heyward. "But he also has bona fide skills that aren't cosmetic. He is one of the best ad-libbers I've ever seen. In terms of how he handles himself, John is doing it the old-fashioned way."

The old-fashioned climb to the top, though, is rockier than it used to be. In a media universe splintered into a thousand parts by cable and Internet outlets, even network correspondents at the White House are less well known than, say, Matt Drudge. While an aspiring anchor must be a good talker and a solid reporter, he or she also needs an X factor--some air of controversy or aura of celebrity--to establish a brand name.

In fact, the next generation of Big Three anchors will never command the mass audience of the Huntley-Brinkley era. The extraordinary longevity of the current crew--Rather, 68, took over in 1981; NBC's Tom Brokaw, 60, in 1982; and ABC's Peter Jennings, 61, in 1983--began at a time when most people got their news from the tube at 6:30 p.m. But even a downsized anchor desk remains the glittering prize.

Roberts seems determined to get there through sheer hard work. When he was tapped as the network's medical reporter, he was known for showing up early at the CBS "fishbowl," the glass-enclosed office where the top producers sit, and pitching the brass on stories. The less charitable explanation is that Roberts is downright neurotic about getting air time.

"Sometimes after three or four days you'd just say, 'John, you have to leave now, enough, go away, we can't take any more,' " says Pat Chevrin, who produces the Sunday evening news. "All people who are as driven as John and as dedicated can't help but drive people crazy sometimes."

Roberts is a pleasant but sober-minded fellow who, Toronto Life magazine once observed, "lacks the gene for irony." He deflects talk about whether he might one day succeed Rather, whose contract expires at the end of next year but who may well continue to anchor beyond that. Roberts insists it's an honor just to be Rather's substitute.

"I'm the sort of person who doesn't want Dan to ever leave," Roberts says. "If he ever left there would be such a vacuum to fill. It would be difficult to be the person on whom that responsibility is placed. It can bring out every insecurity you ever had."

John Roberts? Insecure? This is getting interesting.

The seemingly unflappable appearance is "just a veneer on the outside," he says. "I look at myself on television and think, 'God, why would anybody want to watch you?' Many people tell me I'm too hard on myself. Nobody will beat me up more about something I've done wrong. I'll stay awake nights hammering myself over it."

Conflicting Obligations

Life as a White House correspondent isn't easy in lame-duck land. While it's a "terrific learning ground," Roberts says, "much of what happens here on a day-to-day basis just passes by without a ripple. In the last year of a second term, the president falls pretty low on the radar screen."

Roberts, who lives in Great Falls with his wife, Michele (his high school sweetheart), their 14-year-old son and 8-year-old daughter, keeps a backbreaking schedule. He works five days a week in Washington, then flies every Sunday to New York. He also fills in for Rather 24 days a year, including most holidays. And Roberts feels a bit guilty about his family.

"It does concern me that a large part of my life is going by and I'm missing it," he says. "There's not a lot of time to do some things I should do as a husband and father. When I hear my daughter say, 'When's Daddy coming home?' or 'Why don't we see Daddy more?,' it really hurts. It cuts really deeply."

Roberts displays his obsessive work habits away from the office. Whether they are skiing, sailing or mountain-biking, says longtime pal Scott Maddalene, a home furnishings executive, "he's a student of almost everything he gets involved with. He studies biking maps and books in incredible detail."

And sometimes the news finds him. Last summer, Roberts and his family were vacationing on Martha's Vineyard when the wreckage from John F. Kennedy Jr.'s plane washed up near their slice of the beach. Soon the CBS crews were camped out in his front yard and he was working round-the-clock.

His current career trajectory seems to emulate that of Rather, who held down the White House job while juggling Sunday and sometimes Saturday anchoring duties from 1969 to 1976. Rather had urged Roberts to take the White House assignment.

"CBS News is not a place that anoints someone into any position," Rather says. "Part of our culture is, you earn it. You're expected to pay an exceptionally high price to get promoted to the best assignments. I think John is qualified to do anything we've got, period. That includes this job."

The mantle of heir apparent can be a weighty one, magnifying a journalist's every step or misstep. At NBC, Brian Williams, who fills in for Brokaw and anchors his own MSNBC newscast, has long been seen as the official successor. Rather himself endured years of speculation about whether he or Roger Mudd would succeed Walter Cronkite.

CBS executives are careful to say that no decision has been made and that there are other contenders, such as "60 Minutes II" correspondent Scott Pelley. The most Heyward will say about Roberts is that "we have a couple of people here who can credibly be talked about as ascending to the evening news chair someday, and I'd certainly put him in that category."

For now, even serving as a pinch hitter on the third-place "CBS Evening News" represents quite a journey for someone whose first job was reading hog reports and playing country music at a 5,000-watt radio station in the Canadian town of Owen Sound.

The son of a Scottish immigrant who died when John was 5, Roberts was raised by his British-born mother, who held down such low-paying jobs as drugstore cashier and car dealer receptionist. A born tinkerer, Roberts built Go Karts and competed in motorcycle races.

In 1977 he became a deejay at Toronto rock station CHUM. "When you're a kid, the excitement of rock-and-roll radio is a real aphrodisiac," he says. "Wow--it was like you were a star."

Roberts spent a decade at CityTV, an independent Toronto station, first in entertainment and later as a reporter and anchor. He was then J.D. Roberts, "the cute, long-haired CityTV veejay who schmoozed his way through the 1980s with the likes of singer Cyndi Lauper," as the Toronto Star put it.

CBS reporter Thalia Assuras, who worked with Roberts at CityTV, recalls him as a serious guy. "John hasn't changed very much at all," she says. "He's always been incredibly intense."

In 1989 Eric Ober, then a CBS executive, offered him an anchoring job at the network's Miami station. "He was kind of a young version of Dan," says Ober, now E.W. Scripps's senior vice president for new media. "Great control on the air. The biggest question I had was, he was infotainment. The question was more one of gravity, heft and intellect. I looked him in the eye and said, 'John, you're going to be years paying your dues.' "

Roberts didn't have to be asked twice. "I was always intrigued by America," he says. "You're living so close. If you can make it there, it's the ultimate statement of your ability."

But Roberts had a jarring introduction to the States. Two weeks after arriving in Florida, his wife was robbed at gunpoint in their garage while her brother was forced to lie spread-eagled on the ground. The family was shaken up, and in 1991 they moved back to Toronto, where Roberts became host of the highly rated "Canada A.M." There was some talk that he had acquired an American accent.

He did the things that morning hosts do, from serious interviews to cooking to chatting up the Barenaked Ladies. But he also clashed with co-host Pamela Wallin, who trashed him in her autobiography as an "entertainer" and "insult to viewers." Wallin says Roberts once joked on the air before she left to interview Warren Beatty: "Make sure you don't get knocked up."

Says Roberts: "She absolutely hates me and will take any opportunity to deride me. I learned a long time ago that not everyone is going to like you."

Roberts left Canada after a year and a half when Ober, by then the CBS News president, hired him again as a network correspondent and co-anchor of the 5:30 a.m. news. There was chatter that Roberts was the great white hope. "When he first came to the network, some people didn't take him seriously and tended to dismiss him as someone who hadn't paid his dues," Heyward says.

When WCBS, the New York station, asked Roberts to anchor the local news in 1994, he was attracted by the bigger salary--and felt uncertain about his status at the network. "I've been here awhile and I'm not sure how well I'm doing," Ober recalls him saying.

But Roberts rejoined the network eight months later when a new boss took over at WCBS, and eventually was chosen for the Sunday evening news. "Who could turn down something like that?" Roberts says. "It was a dream come true."

Roberts's resume belies criticism that he's some sort of Ken doll. In 1996, when a bomb exploded during the Atlanta Olympics, he and a colleague stood on a roof and broadcast for 10 straight hours, a performance that won Roberts one of his three Emmys (the others were for coverage of the TWA Flight 800 crash and the death of Princess Diana). Last year, venturing out during a heavy night of U.S. bombing in Belgrade, Roberts was the first to report that the Chinese Embassy had been hit. He's also reported from Uganda, Honduras, Nicaragua, Japan, India and Pakistan.

Roberts pauses when asked if he's had any career disappointments; all he could come up with was losing out to Pelley when the White House job first opened up.

After moving to the medical beat, Roberts, a former pre-med student, devoured scientific journals and consulted experts on how to evaluate them. "He came in not knowing more than the next person about medicine, and after a year he knew everything," says producer Chevrin. "He just doesn't give up. If another medical correspondent scooped him, he would just be furious at himself."

Once, frustrated that they had no pictures when a scientist grew an ear on the back of a mouse, Roberts scrambled to find a similar mouse experiment. "He arranged to have us shoot it so we'd have our own ear," Chevrin says.

Roberts may be right that he's not quite ready for stardom--his clothes were considered so jumbled that a CBS executive began advising him on his wardrobe--but he's clearly shining these days. He's even got a home gym--where he runs, bikes, does biceps curls and abdominal crunches--to avoid any excess anchor-flab.

"I've got some things to learn," Roberts insists. "I don't want it to happen fast."