He first got interested in singing by a country-oriented musician called Doug Fowlkes, who was in a band called the Airdales (United States-navy slang for Navy pilots). The song"s success led to a 1967 motion picture of the same title, starring Roberts. He appeared subsequently in several other Italian films.
He was known for always wearing dark sunglasses.
Roberts sang the Luis Bacalov-written theme song from the 1966 film, Django. Quentin Tarantino reused the recording as the opening theme for his 2012 film Django Unchained.
He died of lung cancer in Rome in 2005.