Born into a Jewish merchant family in Pest (part of the Austrian Empire at the time), he left the city at the age of seventeen in order to attend the Vienna Academy of Fine Arts, where he studied archaeological drawing (graduating in 1839) and made his first Romanian acquaintance, the painter Ioan D. Negulici.

[2] In 1846, the profit from his works afforded him a trip to England; upon his return to Paris, he was informed of his family's financial destitution, and left for Budapest in early 1847, only to leave in summer for Mehadia, and then, in August, for Bucharest.

[3] On June 18, 1848, soon after the Provisional Government took hold, Rosenthal applied for Wallachian citizenship (in theory, Romanian - as the new administrative body indicated its goal in the union of the two Danubian Principalities); the document giving him the right of naturalization justified it as "taking in view his talent and the active part he played in the revolution".

[5] The Government assigned him the designing of a triumphal arch in Bucharest, one meant to mark the success of the revolution, and, probably, of a Statue of Liberty (the latter project only survives in a watercolour by Theodor Aman, Dezrobirea Ţiganilor - "The Freeing of the Gypsies").

His plan was divulged by spies of the Second French Republic (already under the authority of Prince-President Louis-Napoléon Bonaparte), who read Rosenthal's correspondence in Paris; the Austrians arrested the painter during his presence in Pest-Buda, citing his "imprudent political statements".