He worked at the State Theatre in Darmstadt, where, on 12 April 1923, he conducted Hagith by Karol Szymanowski, and at the State Opera in Wiesbaden, where, on 6 May 1928, he conducted the premiere of three short operas by Ernst Krenek: Der Diktator, Das geheime Königreich, and Schwergewicht, oder Die Ehre der Nation, as part of the Maifestwoche festival.
Returning to Germany, he worked in Mannheim and, from 1933 to 1936, as conductor of the Berlin Jüdischer Kulturbund, notably conducting the (all-Jewish) German premiere of Verdi's Nabucco on 4 April 1935.
[5] He remained in Tokyo until 1946 and, while he was there, he taught Hideo Saito (conductor, educator and co-founder of the Toho Gakuen School of Music), Masashi Ueda (conductor of the Tokyo Symphony Orchestra, who introduced contemporary Russian, American and Japanese music to the public), and Roh Ogura how to conduct Beethoven's symphonies.
He served in that post for four seasons, continuing Halász's innovative programming of unusual repertoire mixed with standard works.
[6] Rosenstock was also the first NYCO director to include musical theater in the company's repertoire with a 1954 production of Jerome Kern and Oscar Hammerstein II's Show Boat.