On the one hand, he was extremely dedicated to achieving unconditional surrender. On the other hand, he was more willing to work with Stalin (afaik) than Truman, and Byrnes would never have become Secretary of State. Would FDR living to the end of WW2 have changed the outcome of the war with Japan?
He still would have dropped the bombs, but he was also the only one who could have put all of America's nuclear weapons under international control and stopped the arms race. Like if Henry Wallace tried that he would almost certainly have been couped. And while there is no universe where Truman would have considered it, even if he offered the Soviets didn't trust him or America enough to follow through.