Marthaniel "Marcus" Roberts was born on August 7, 1963, in Jacksonville, Florida. His mother was a gospel singer who had herself gone blind as a teenager, and his father worked as a longshoreman. Roberts lost his sight to glaucoma and cataracts and has been blind since the age of five. He began by picking out notes on the piano at his church, taught himself on the instrument his parents bought when he was eight, and had his first lesson at twelve. He attended the Florida School for the Deaf and the Blind in St. Augustine, the school where Ray Charles had been a student, and at eighteen began classical piano study at Florida State University with Leonidas Lipovetsky. In 1982 he won the Young Artist's Award at the National Association of Jazz Educators conference.

In 1985 Roberts left Florida State to join the band of Wynton Marsalis, replacing Kenny Kirkland as its pianist at the age of 21. He stayed more than six years, becoming the quartet's second major soloist and a hub of its rhythm section, and he plays on Marsalis albums from J Mood to The Majesty of the Blues. In 1987 he won the first Thelonious Monk International Jazz Piano Competition, and in 1988 he signed with Novus, the RCA/BMG jazz imprint. His debut, The Truth Is Spoken Here (1989), brought in Marsalis, drummer Elvin Jones and tenor saxophonist Charlie Rouse, and Deep in the Shed (1990) followed with a larger ensemble that included trombonist Wycliffe Gordon. Alone with Three Giants (1991), a solo-piano album of music by Jelly Roll Morton, Duke Ellington and Thelonious Monk, made his commitment to the older tradition plain. Delfeayo Marsalis produced his Novus albums.

In 1992 Roberts made his first appearance as a soloist with a symphony orchestra, under Marin Alsop, and early in 1994 he moved to Columbia. Gershwin for Lovers (1994) paired him with bassist Reginald Veal and drummer Herlin Riley. In 1995 he formed a trio with bassist Roland Guerin and drummer Jason Marsalis, the youngest of the Marsalis brothers, and the group recorded Time and Circumstance (1996), In Honor of Duke (1999) and Cole After Midnight (2001), working on a concept in which bass and drums share equal control of tempo, texture and form. Portraits in Blue (Sony Classical, 1996), his first recording with an orchestra, included Gershwin's Rhapsody in Blue and James P. Johnson's Yamekraw and earned a Grammy nomination. Blues for the New Millennium (1997) used a large ensemble that included saxophonist Ted Nash and drummer Ali Jackson, and The Joy of Joplin (1998) was a program of Scott Joplin's music recorded in Tallahassee.

Roberts started his own label, J-Master Records, in 2009, and released New Orleans Meets Harlem, Vol. 1 that year, with music by Joplin, Ellington, Morton, Monk and Fats Waller. Celebrating Christmas (2011), which credits Rodney Jordan on bass, and From Rags to Rhythm (2013) followed. In 2012 the trio toured and recorded Across the Imaginary Divide with banjoist Béla Fleck, and in 2013 Roberts and the trio reunited with Marsalis for Together Again, issued as separate studio and live albums. He formed the Modern Jazz Generation, a multigenerational band whose Romance, Swing, and the Blues came out in 2014, and his Trio Crescent: Celebrating Coltrane followed in 2017.

His concert-hall work has run alongside the club and studio records. In 2003 he premiered his arrangement of Gershwin's Piano Concerto in F with the conductor Seiji Ozawa, first in Japan with the New Japan Philharmonic and then in Europe with the Berlin Philharmonic at the Waldbühne, a performance released on DVD as A Gershwin Night. His first piano concerto, Spirit of the Blues, co-commissioned by the Atlanta Symphony Orchestra and the Savannah Music Festival, was premiered in April 2013 under Robert Spano, and a second, Rhapsody in D, commissioned by Ozawa and the Saito Kinen Orchestra, in 2016. CBS's 60 Minutes profiled him in 2014. His honors include the Helen Keller Award for Personal Achievement (1998), the Dorothy and David Dushkin Award from the Music Institute of Chicago (2024), and honorary doctorates from the Juilliard School, Bard College and Brigham Young University. In March 2026 the Cincinnati Pops released Harlem Renaissance, an album built around his arrangement of Yamekraw, with Roberts, his trio and the Modern Jazz Generation. As of 2026 he is listed as Professor of Jazz Piano on the faculty of the Florida State University College of Music, and his own site also names him a Distinguished Professor of Music at Bard College.

Roberts plays in a tradition-first idiom. Critics place his models in Jelly Roll Morton, Fats Waller and Thelonious Monk rather than in the modal and post-bop pianists of the 1960s, and his stride and ragtime emphasis, set on a gospel and blues grounding from his Jacksonville childhood, drew sharp criticism in some quarters of the jazz press, as did the Marsalis-school neo-traditionalism around him. His trio concept, which his own site traces to orchestral devices borrowed from the Ahmad Jamal trio, with the swing of the Oscar Peterson trio and the buoyancy of Erroll Garner behind it, gives bass and drums equal power to change tempo, groove and form in the middle of a piece. He has also written long-form works for orchestra and big band, and he is a committed mentor: his own site lists Nicholas Payton, Marcus Printup, Ronald Westray, Vincent Gardner, Roland Guerin, Etienne Charles and Jason Marsalis among the players he has trained or guided. AllMusic's biography sums up the debate over his work as whether he is a dedicated preservationist or an unrepentant nostalgist.