Sessions was born in Brooklyn, New York, to a family that could trace its roots back to the American revolution. His mother, Ruth Huntington Sessions, was a direct descendent of Samuel Huntington, a signatory of the Declaration of Independence. Roger studied music at Harvard University from the age of 14. There he wrote for and subsequently edited the Harvard Musical Review. Graduating at age 18, he went on to study at Yale University under Horatio Parker and Ernest Bloch before teaching at Smith College. With the exception, mostly, of his incidental music to the play The Black Maskers, composed in part in Cleveland in 1923, his first major compositions came while he was traveling Europe with his wife in his mid-twenties and early thirties.
Returning to the United States in 1933, he taught first at Princeton University (from 1936), moved to the University of California, Berkeley, where he taught from 1945 to 1953, and then returned to Princeton until retiring in 1965. He was elected a Fellow of the American Academy of Arts and Sciences in 1961. He was appointed Bloch Professor at Berkeley (1966–67), and gave the Charles Eliot Norton Lectures at Harvard University in 1968–69. He continued to teach on a part-time basis at the Juilliard School from 1966 until 1983.
For a list of his notable students, See: List of music students by teacher: R to S#Roger Sessions.
In 1968 Sessions was awarded the Edward MacDowell Medal for outstanding contribution to the arts by the MacDowell Colony. Sessions won a special Pulitzer Prize in 1974 citing "his life's work as a distinguished American composer." In 1982 he won the annual Pulitzer Prize for Music for his Concerto for Orchestra, first performed by the Boston Symphony Orchestra on October 23, 1981.
He died at the age of 88 in Princeton, New Jersey.