Rosen, along with Martin Bromley, Ray Lemaire, and Dick Dodderer, played a key role in the establishment of Sega, originally created as Service Games to work with arcade machines, and later becoming a major player in the home console market.
In an interview with Next Generation Magazine in 1996, Rosen recalled:
Arcade machines were an immediate and huge success. It is embarrassing to say, but the payback usually occurred in less than two months.
During that period, I was opening shooting and hunting game parlors all over Japan, and we were lucky... I don't remember exactly how many there were, but by the time I left, there wasn't a single city that didn't have at least one of our parlors.
Rosen continued to lead Sega until its buyout by Gulf+Western and helped establish Sega of America. Under his leadership, the company released the SG-1000, Master System, Mega Drive/Genesis, Game Gear, Saturn, and a range of accessories.
He noted:
Sega has been involved in video games almost since their inception. We started producing our own games shortly after importing Pong.