Friedrich's mother Serena Anna, daughter of Ignaz Moscheles, came from a British scholarly family of Jewish faith (who had converted to Christianity).
After a dispute with the university department leadership in 1890, he gave up his academic position, and as his father before him he entered a career at the Foreign Office.
In 1890, he published Modern Persian Grammar, with Nāsir al-Din Shāh, the Shah of Iran, as co-author; parts of the diary of the latter were employed as texts.
Moreover, like his friend Wilhelm Solf, he held liberal views, and simultaneously supported the monarchy and was an anglophile, and thus was considered as the right person for achieving an understanding with Britain.
Rosen retired in protest against the London ultimatum, in which the Allied powers combined demands of high reparations from Germany with threats of sanctions.
Rosen became chairman of the German Oriental Society, the umbrella organization of the Orientalists in Germany, and dedicated himself increasingly to scientific work.
Since the seizure of power by the Nazis, whose ideology Friedrich Rosen opposed from the beginning, the former Foreign Minister was subjected to anti-Semitic hatred, because of his descent.
Because of the racist policy of the Nazi regime, the younger Dr. Rosen, who was sending reports to the German Foreign Ministry in Berlin about the Nanjing Massacre, was forced to retire from the diplomatic service in 1938.