Rosen's family moved to Long Beach when he was age 7 and he graduated from Long Beach State by 1963. Shortly after he got a job at KCET as a production assistant. In 1965, channel 2 was looking for a kid's show, so Rosen pitched
Dusty's Treehouse (1968) to CBS and ended up doing the show for 10 years. In the early '80s, Rosen was involved in several cable startups at the dawn of a new generation. He was also the casting director for
Teenage Mutant Ninja Turtles (1987) and the voice director for several hit cartoon shows such as
Mask (1985),
My Little Pony: The Movie (1986),
Captain N: The Game Master (1989),
Defenders of the Earth (1986), and
Fraggle Rock (1987).
Entering the '90s he was the voice director for computer game
Gabriel Knight: Sins of the Fathers (1993) and also did the voice for Yuri Markarov in
Quest for Glory IV: Shadows of Darkness (1994).
Over his career, Rosen won several Emmys; ten L.A. Emmys and the George Foster Peabody Award.