Rojahn is a surname. Notable people with the surname include:
Birgitte Cornelia Rojahn ( Gulbrandsen; 1839–1927), Norwegian stage actress, concert singer and voice trainer, wife of Ferdinand A. Rojahn (1822–1900), German musician, organist, violinist and conductor
Also Ernst Rojahn (1909–1977), Norwegian chess player
See also Rojan (disambiguation)