Robertson graduated from the University of Western Australia in 1965 and taught at various institutions, including drama at Antioch College in the U.S.A. and at Flinders University. It was at Flinders that he began adapting and directing plays. In 1972 he joined the Australian Performing Group at the Pram Factory Theatre in Melbourne where he acted, wrote and directed. He made his first appearance in a television series Rush in 1974, which was followed by a role in the film The Cars That Ate Paris (1974). Robertson's numerous acting credits cover film, stage and TV. He also scripted educational videos such as Ride an Ag Bike - and Survive (1989). Robertson co-authored with his History of Australia : The Musical (1995) collaborator Martin Armiger to write The Truth about the Protection Racket : A Living Newspaper or Didactic Entertainment, Running Down Censorship of the Media in Australia [1971], which appears never to have been produced.