He was also head of the agricultural colony of the Jewish Colonisation Association, created by Baron Maurice de Hirsch, in Woodbine (New Jersey).
Beginning in 1921, he was the envoy of Joint in Russia and the representative of Joint in the American Relief Administration;[5] from 1924 to 1938 he was director of the Agro-Joint Corporation, which aimed to transform Soviet Jews, mainly "Lishenets"s, into peasants ... Rosen believed that the secret of a happy future for the Jewish people under Soviet rule was in "productivity", that is, in the transition to productive labor.
[6] During the years of the Great Terror, both of Rosen's deputies for Agro-Joint were arrested — on November 27, 1937[7] Ezekiel Abramovich Groer (1886—1938), and on March 27, 1938 — Samuil Efimovich Lyubarsky (1878—1938).
As the director of Agro-Joint, I consider it my duty to declare that if any illegal actions are found in the work of our organization in the USSR, then I am personally responsible for them, and not our employees and not my deputies.
I hereby ask you to give me the opportunity to testify to the relevant Soviet authorities on all issues related to the activities of our organization in the USSR, and I agree in advance not to resort to the protection of any diplomatic sources, since the matter concerns me personally[10]"According to the recollections of the daughter of Ezekiel A. Groer, Rosen even managed to meet with Vyacheslav Molotov, but Molotov said that he could not do anything, since Rosen's former Agro-Joint employees had already confessed to everything.
[3] In 1939, Rosen, on behalf of Joint, investigated the possibility of establishing settlements for Jewish refugees from Europe in British Guyana and the Dominican Republic.