Rosoff first launched Arnold & Co in Boston just after the Second World War, with Stop & Shop and John Hancock among the agency's first clients.
Over the years, Rosoff was credited with helping Arnold & Co become a major competitor in the US advertising industry, notable for its long-standing relationships with key clients and employees.
Rosoff retired from Arnold & Co in 1985, by which time the agency was claiming around $50 million in billings.