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. In 1956, Roberts returned to the Olney Theatre, starring opposite Jan Farrand in Much Ado About Nothing with the Players, Inc. group. The same year, Roberts made his television debut in the "Shadow of Suspicion" episode of Kraft Television Theater, followed by guest-starring roles in Whirlybirds, Gunsmoke, Cimarron City, Buckskin, Sugarfoot, and Cheyenne. Roberts signed a contract with Columbia Pictures in 1957, and made his film debut a year later as one of Burl Ives' contentious sons in Desire Under the Elms (1958). The film was nominated for a Best Cinematography Academy Award. He also landed a character role in The Sheepman (1958), opposite Glenn Ford and Shirley MacLaine, and continued to guest-star on television shows such as episodes of Shirley Temple Storybook Theater ("The Emperor's New Clothes", "Rumplestiltskin", "The Sleeping Beauty", and "Hiawatha"), the live-broadcast Matinee Theater, where he starred again in Shakespeare's Much Ado About Nothing, and in The Heart's Desire. This was followed by appearances in Trackdown, Buckskin, and episodes of Zane Grey Theater. Roberts guest-starred as Captain Jacques Chavez on the NBC adventure series Northwest Passage (1958). He appeared with fellow guest star Fay Spain in the 1958 episode "Pick Up the Gun" of Tombstone Territory and played the lead villain in the 31st episode ("Hey Boy's Revenge") of Have Gun – Will Travel, portraying a killer boss exploiter of Chinese coolie laborers. In 1959, Roberts guest-starred in episodes of General Electric Theater, Cimarron City, Sugarfoot, Lawman, One Step Beyond, Bronco, 77 Sunset Strip, The Detectives, and House Call. Also in 1959, he co-starred in the film Ride Lonesome. "If Roberts felt typecast by Westerns, they also provided his finest role in this film, arguably the greatest of the B-movies starring Randolph Scott and directed by Budd Boetticher. Roberts recognized the film's classic structure; his engaging outlaw, Sam Boone, counterpoints Scott's granite-faced Ben Brigade, maintaining the tension of whether they will work together or clash. He similarly played off James Coburn, who was making his film debut as Boone's quiet sidekick, Whit." The same year, he was cast in Bonanza. Bonanza Roberts played Ben Cartwright's urbane eldest son Adam, in the Western television series Bonanza. Unlike his brothers, Adam was a university-educated architectural engineer.