What's an ex-rock 'n' roller do when he enters mid-life?If he's Bobby Poe, an Oklahoma boy who used to sing a mean Elvis and Jerry Lee Lewis imitation, he runs one of the country's three record tip sheets from a Georgetown office above a poodle grooming shop.

"I always admired the guy behind the desk with the cigar and the beautiful secretary sending me off to Red Bluff, Montana, in February with ten feet of snow," says Poe 42, formerly of Bobby Poe and the Poe-Kats. "I wanted to be the guy behind the desk."

Poe, as the saying goes, came close, but no cigar, as a singer, songwriter and manager during two decades of aiming toward American Bandstand. He managed a group, the Chartbusters, who enjoyed a couple of hits, including "She's the One." He wrote five songs for Fats Domino. Then in 1968 he got his desk job, publishing the Bobby Poe Report, a personal pick of future hits to guide AM radio music directors.

"Each station is fighting for ratings and they can't afford to be wrong on records and they can't afford to get a record too late," says Poe, who sends out 800 copies of his report each Friday. Half of his customers - mostly record promoters - pay $135 a year, and half - mostly radio personnel - receive the report gratis. Cooperative disc jockeys around the country provide Poe with names of their hot records, which he contends makes his list more prescient than trade publications such as Billboard and Cashbox, which rely on confirmed sales to rate a record's popularity.

Personally, Poe favors Frank Sinatra, but the hits just keep on comin', so each week Poe tells his subscribers about several "guaranteed" blockbusters. Three weeks ago, he predicted - guaranteed, even - these songs would be contenders this first week of February: Art Garfunkel's "Wonderful World," Barry Manilow's "Can't Smile without You," and Abba's "The Name of the Game."

What if he's wrong?

"Once I guarantee 'em," says Poe, "they're supposed to be hits."