Born in Trnjani (today Ukraine). Studied in Zagreb and Vienna (1928-1932), was an opera singer, and performed across Europe. Immigrated to the U.S. in 1955, where he taught voice at Indiana University. Rothmüller composed chamber and choral music, and Sephardic and Ashkenazi songs. According to Eliot Kahn, Rothmüller identified 20 of his compositions as Jewish music. As an author he published The Music of the Jews.