In 1960, he was appointed to the Yale Medical School faculty. During early years at Yale, he was supported in research and teaching by two successive 5-year federal Research Career Investigator Grants. There was an interruption of two years when Rothenberg served as Captain in the U.S. Army Medical Corps as Chief Psychiatrist for American military personnel in Puerto Rico and the Caribbean area. For this service, he received both a Letter of commendation and a Certificate of Merit. He then returned to Yale Medical School, where he remained for nearly 20 years.