I just finished reading a Hank Greenberg biography. In it, he and Rosen majorly clashed when negotiating salary, and when Rosen refused to take a huge pay cut for a mediocre year, Greenberg refused to trade or release him, and Rosen's career ended prematurely. Pretty sad story.
Rosen also dealt with a lot of crap for being a Jew, especially when he replaced Ken Keltner, a Catholic, at third. I think he also was one of Steinbrenner's early GMs.
RIP