Rosenberg fought as a professional boxer from 1919-1925 and held the NYSAC middleweight championship briefly in 1922 when he defeated Phil Krug for the vacant title on August 14, 1922 at the Veledrome in Brooklyn, New York City. This championship garnered the attention of Mike O'Dowd, and the two scheduled a fifteen round fight at 160pounds. Losing that fight, Rosenberg became one of the shortest reigning champions in boxing history, having only held his championship for 109 days before his defeated by O'Dowd.