[2] Due to financial problems, he was forced to leave school by eighth grade to help support his family, who had lost their store during the Great Depression.

After several jobs, at age fourteen, he went to work for Western Union as a full-time telegram delivery boy.

At seventeen, he started working for Simco, a company that distributed ice cream from refrigerated trucks, rising from delivery boy to national sales manager at age twenty-one, supervising the production, shipping, cold storage and manufacturing and managing 40 to 100 trucks.

In 1955, upon opening his sixth shop, he decided on the concept of franchising his business as a means of distribution and expansion.

[4] In the early 1960s, Rosenberg founded a fast food chain, Howdy Beefburgers (later Howdy Beef n' Burger), in Massachusetts, locating many of its restaurants beside Dunkin' Donuts shops so they could share common parking lots to compete with larger chains such as McDonald's for retail space and customer draw.

[3] In 1980, he donated Wilrose Farm to the University of New Hampshire,[4] and later became involved in philanthropy, primarily benefiting hospitals.