Three years ago, pianist Marcus Roberts was at a crossroads.

That he was a good musician was not in doubt: Ever since he was an 8-year-old growing up in Jacksonville, sneaking into church to play the organ, people knew he was gifted. He'd begun formal training at age 12, and by the time he was 20, he'd won numerous local competitions, been recognized by the governor of Florida for his musical talents and established himself as one of the top music majors at Florida State University in Tallahassee. He had technique and style. People knew him as Marcus Roberts, the heavyweight jazzman. But Marcus Roberts the musician knew better.

Even as a teen-ager, Roberts knew that jazz wasn't something a musician just pops into his repertoire. It was too difficult, too complex; too serious. He'd heard Charlie Parker blow and decided that for someone to be able to play that well was not simply a matter of God-given talent, but of devotion to the music. He'd heard Thelonious Monk and knew that music like Monk's came not so much from heavenly inspiration as from earthly elbow grease -- devotion and practice. More practice than folks would ever fully appreciate. More practice than he believed possible. Yet Roberts knew that if he were going to play jazz like Bird, like Monk, like Art Tatum and the other artists he admired, then he'd have to find a way. Because a real jazzman plays. A phony jazzman just acts like he can play.

So every day, Marcus Roberts the musician sat down at his piano, and eight hours later Marcus Roberts the jazz musician would get up and find himself a little closer to the truth. "You can't kid yourself," he says. "I knew what I needed to do and what I needed to do to get there."

Now, at 24, he's there. The winner of the first Thelonious Monk International Jazz Piano Competition held last November at the Smithsonian, Roberts is a sideman with the Wynton Marsalis quintet and is considered one of the top young jazz pianists in the country. He performs this afternoon at the Presidential Ballroom of the Capital Hilton Hotel as part of a double bill presented by the Beethoven Society and the Thelonious Monk Center for Jazz Studies. Opening the concert will be Glenn Sales, winner of the first Beethoven Society Classical Piano Competition in 1978.

"At some point, you have to deal with the pain of recognizing your flaws," Roberts says, looking back. "People only want {to see} what's right about themselves. They don't want the responsibility of accepting what's wrong with themselves. Monk, with all his abilities, he could have sold out easily. But he had such a great amount of personal integrity, he was not willing to compromise. In the end, it's better to face the truth about yourself. You're better off."

The slender jazzman sits on the edge of the bed in his suite at the Vista International Hotel, hands clasped under his chin, face pointed straight ahead in thoughtful repose. Blind since early childhood, he keeps his dark glasses on. With his sharp features, well-defined jawbone, slim fingers, close-cropped hair, white wool sweater and clean white tennis shoes, he looks like a young attorney about to go for a Sunday stroll with his kids. A week before the Hilton show, he's in town for a gig at Takoma Station with the Marsalis band. The trumpet baron has just walked out of the room, having stopped by to trade quips with Roberts.

"I'll always have a tremendous love and respect and loyalty towards Wynton," says Roberts, who began playing with the quintet in 1985. Marsalis first heard him perform in 1982 in Chicago, where Roberts was performing for a jazz educators' convention. When pianist Kenny Kirkland left the Marsalis unit, Roberts got the call.

On the road most of the year, the two can often be seen together -- walking through hotel lobbies, clubs and concert halls, chatting and laughing at some private joke, the hornman leading the pianist by the elbow. Says Marsalis: "Marcus is the first guy I met in my generation who is serious about music. When I called him for the gig {in May 1985}, he knew my music by heart. And there's no way he could learn that music other than by hearing it. He's an intelligent, soulful man."

Last November Roberts wowed the audience at the Monk competition, where 22 pianists from around the world competed for $18,000 in prize money. One of the last contestants to arrive, he'd come in on a rocky, delayed flight from Alaska, where he had played the previous night. His performance of "Round Midnight" and "Blue Boulevard Blues-R" won him the $10,000 first prize, not to mention the adulation of the packed house at the Museum of Natural History's Baird Auditorium.

He entered the competition "to force myself to get more understanding of Monk's conception as a musician," Roberts says. "His music is so complex, you have to overcome your fear of taking it on ...

"His music can be dug from any level -- the blues, the intellect, the sense of history. He dealt completely with the vocabulary of the horn players before him. It's a world of music -- like Beethoven. When you say Monk, you're not just saying someone who played the piano, even though his piano styles were unique. Monk is what a jazz musician strives to become."

Roberts has a great deal of Monk in his playing. Like the master, he is spare and thoughtful -- a welcome contrast to the hordes of young jazz pianists who churn out textbook licks likemachines pumping out bubbles. Yet he's unafraid of lush chords and full, fat sounds, willing to explore new turf and possessed of the technical ability andmusical common sense to make whatever he does -- even the most complicated things -- sound simple and pure.

The youngest of two boys in a working-class family from Jacksonville, he inherited his musical vocation from his mother, a gospel singer, and his soft-spoken pride and resilience from his father. "I never saw my father complain about anything," he says.

"You're dealt a set of circumstances in life. I was taught: Be a man. Deal with it. There were no jazz clubs when I was coming up. No opportunities to play. But my family supported what I was doing. They taught me to appreciate what true love and loyalty can do. My mother lost her sight at the age of 15. I lost mine when I was 4. So I could never say that someone didn't understand."

He sits thoughtfully, choosing his words with care, yet they flow easily from him. "Everyone has a set of circumstances they deal with in life. These circumstances can control you, or you have a responsibility to figure out how you'll deal with it. I've always tried to follow God and the truth, because the truth is always the most positive thing, and I know God has a plan for me."