(written from a Production point of view)
Robertson was among the very first African-American network executives in American television. He was approved by Gene Roddenberry to serve as Program Manager for Star Trek, although the production staff later regretted this decision, as they've found Robertson and his constant meddling with the show to be hard to deal with. (Inside Star Trek: The Real Story, pp. 140-142)
Robertson later served as Vice President of Motion Pictures for Television at NBC, after which he resigned in 1976. He formed his own production company and worked as a producer. He was also an executive in Bill Cosby's production company. Robertson died in his Bel Air home in 2011.