ROY SCHEIDER sits coiled in quiet, unnoticed, with his morning coffee and newspaper amid the cacophony of a New York coffee shop, just a few blocks from where his new film, "All That Jazz," is playing to packed houses.

Although the strict routine of his life sends him there every morning, no one -- not even the regular 9 a.m. coffee crowd -- notices the actor in his sweat suit and tennis shoes. Not even when his lipline breaks across his lean, tanned jaw like an earthquake fault, finally erupting into a deep gorge grin and laugh as he jokes about playing bait to a 2,000-pound shark.

"When 'Jaws' broke, a couple of mornings later I got up and roamed around the bedroom and said, '---- 'em all'. If they don't think that's a good performance then what the hell am I doing?" he says, recalling the reviews. "One of the reasons no one noticed me is because I play the audience. In that film I am the audience, so I just get washed aside."

But that was four years ago. Now, at 46, Roy Scheider is finally coming into his own -- known and respected as a serious dramatic actor instead of the co-star of a fish. In "All That Jazz," Scheider dominates the film, playing the burned-out womanizer and choreographer Joe Gideon, a character modeled after Bob Fosse. Within 10 days of the film's New York release, he opened on Broadway, playing a cuckold in Harold Pinter's comedy, "Betrayal," which has received almost universal praise from the New York critics.

He has finally escaped the tough-guy film roles his face had trapped him in. "This is a different plateau," says Scheider, wearing a set of glasses with frames as big as dollhouse windows. "It's the place I've always wanted to get to. It's the place where people say: 'Hey -- this guy is an actor! He can do this and he can do that -- he can surprise us.' People say, 'Wow, it's not him.' That's the fun of acting, to be able to crawl into someone else's personality. And now I have more of a chance to do that than ever before."

But it wasn't easy to get the role in "Alll That Jazz" -- and not easy for Bob Fosse to choose a person whom he had never met, and whom one of Fosse's friends described as "leftover Chicken of the Sea?" (Richard Dreyfuss was first offered the role but declined.) Fosse himself admitted to Scheider on the set that another friend had confided to the director weeks before, "You'll be committing professional suicide if you choose Roy Scheider."

"I knew none of this until after the show started," says Scheider, his distinctive chin hanging over the coffee cup. "But Fosse and about two other people had an idea that I could possibly play this part, and that's all. He hung onto me against a lot of opposition."

("Scheider is a very athletic guy," says Fosse. "He's really into physical stuff. You can't find a dancer around who can act. Barry Bostwick, but he's too young. Gene Kelly in his prime. Ain't nobody around like that that I know of.")

Scheider says: "I think he chose me first of all because he knew I had a certain kind of humor and a certain kind of physical likeness to what he felt a choreographer should look and move like. He just held onto that decision."

That "certain kind of humor" may be a product of his personal history. Born in Orange, N.J., and raised nearby, Scheider was bedridden with rheumatic fever at age 7. He devoured books and newspapers, and when he was able, watched sports and went to Saturday matinee movies, developing a love of literature and theater and a desire for exercise.

At Franklin and Marshall College, he acted in student productions. Producer Joseph Papp read an enthusiastic review of one show and was impressed enough to invite the young Scheider to New York. From his first performance as Mercutio in "Romeo and Juliet," Roy Scheider was set on a career as an actor. But it would be 20 years and acores of acting roles later before he would achieve financial success in film.

The reason was his face. "After my first role in New York, I went into the Air Force for three years," he says. "By the time I got out, my whole demeanor, my face, had become -- well, arcane is the word. I was immediately cast in tough lawyer roles, cops and criminals. Suddenly, as far as films went, I was in the underworld. The only place I could keep doing what I wanted to do was in repertory.

"Hollywood was going on first impression, which was "The French Connection,' where I played a smuggler, and 'Klute,' where I was a pimp. Those people in Hollywood don't have any imagination. They figured, "Hey, Scheider is a tough guy.'"

He finally broke out of the mold as the romantic lead in "Sheila Levine Is Dead and Living in New York." The reviews of his performance were favorable, but the movie was a bust, and he went back to tough guys in such films as "The Supercops."

During those two decades, Scheider began another routine: exercise. He has a special love for boxing, and attributes his distinctive nose to a short boxing career, in which he lost his second and final fight. But even now in his 40s, married to Cynthia Begout (senior film editor on "Breaking Away"), and with a 15-year-old daughter, Scheider still talks about his daily jogs through Central Park and his workouts at a locall gym on Manhattan's upper East Side as the high point of each day. He compares the day he did a handstand on the rings to the success of "All That Jazz." He is governed by routine, he admits, right up to showtime. And it is fitting that both of the roles he is currently starring in are characters who worship routine almost to the point of denying everything else.

"Both Gideon ['All That Jazz'] and Downs ['Betrayal'] are very, very much into discipline, a certain kind of discipline you have to have in order to get the work done," says Scheider. "And I believe in that. I believe that is true. I don't think you can come zipping into the theater 20 minutes before curtain time and give a good performance.

"It's a disease all artists have in common -- to perfect your work and prepare yourself. If you want to be the best, you've got to get up earlier, work harder and rehearse better."

Nonetheless, he says, "there were times this past year when I was very busy because right after 'All That Jazz' I went into 'Betrayal,' and I began to think, 'Jesus, I'm working and rehearsing all the time. Is this all there is?' But then I ask myself, 'What do other people do? They're going 9-to-5 all over the country.' I relealize that I am not the habitual workaholic but that I am happiest when I have work to do."

Scheider decided to do "Betrayal" because of "a basic desire to get back to the discipline of the theater" (seven years ago, the last play he was in closed after one performance). He has found that he cannot exist on a diet of film alone. His success in "Betrayal" surprised him, much as the success of "Jaws" did four years ago after he had overheard a young director named Steven Spielberg talk about his fish adventure at a Hollywood cocktail party.

"I heard this guy talking about a film where a fish sinks a boat, says Scheider, grinning. "And I thought to myself, 'Boy, there's a director in trouble. Who will he ever find to play in that film?'"

But for the same reason "Jaws" proved beneficial for Roy Scheider after years of anonymity, it proved destructive as well. Forty million people saw Scheider in his routine, one-dimensional role. And that's why Roy Scheider, when he rises out of bed these days for his morning jog, feels that "extra tinge that adds spriteness."

"Up 'til now a lot of people didn't know," says Scheider. "I've known what I could do and couldn't do. Now they know. But for the ones who thought I couldn't, I give a little extra kick for them."