Second-only to Robert Fuller, Roberts ranked second for guest-starring in a number of Western shows.
The last surviving original "Bonanza" (1959) cast member to die.
The only "Bonanza" (1959) actor to have lived a long life, next to Lorne Greene, who played his TV father in the series.
The singer appeared in one-act operas and ballets with the North American Lyric Theatre early in his career.
Updated his George Fallon character on an episode of "Diagnosis Murder" (1993), he played decades after "Mannix" (1967).
Upon his death, he was cremated.
Was a spokesperson for the National Kidney Foundation in the 1980s.
Was also a good friend of the late Michael Landon. Roberts attended his funeral on 5 July 1991. Both Landon and Roberts co-starred together on "Bonanza" (1959).
Was also a lifelong activist, which included participation in the Selma to Montgomery Marches in 1965, and pressuring NBC to refrain from hiring whites to portray minority characters.
Was good friends with Peter Graves, Raymond Burr, Henry Darrow, Burl Ives, James Best and Robert Vaughn.
Was the only original cast member of "Bonanza" (1959) to have become an accomplished singer, though David Canary, who joined the show in 1967, had a background in voice and performed on Broadway.
Was the spokesperson for Ecotrin Tablets between 1982 to 1990.
When he was interviewed after his career resurgence with "Trapper John, M.D." (1979) in the early 1980s, Roberts identified himself as very much a liberal.
When he won the role as Adam Cartwright on "Bonanza" (1959), he found the adjustment to a television show difficult.
While serving for two years in the United States Marine Corps, he participated in the Marine Corps Band.
With his G.I. bill, he attended the University of Maryland, where he was drawn to acting, eventually leaving school to work for the stage.