In 1952, Roberts moved to New York, where he appeared first off-Broadway in one-act operas and ballets with the North American Lyric Theatre, with the Shakespearewrights, at the Equity Library Theatre, and later on Broadway with performances in "Tonight in Samarkand" (also in Washington, DC), "The Lovers" opposite Joanne Woodward, and "A Clearing in the Woods" with Robert Culp and Kim Stanley. He won a Drama Desk Award in 1955 for his performance in an off-Broadway rendition of "Macbeth", which was followed by the role of Mercutio in "Romeo and Juliet". He performed in "Twelfth Night", "The Merchant of Venice", "Dr. Faustus", and "The Taming of the Shrew" at the American Shakespeare Festival, and later on Broadway. He performed in "St. Joan" (1954, Cleveland), "Down in the Valley" (at the Provincetown Playhouse), "The Duchess of Malfi", "Measure for Measure", and "King John".