There are a few places in Ralph Erkelenz's Ben-Hur essay where it seems impossible to tell who added or changed some detail. Rozsa touching up or correcting Zador's work? Maybe, but you you would sketches and other score versions together to make sure. Christopher Palmer, who worked with many composers (and who is credited as "assistant" rather than orchestrator on the late films), confirmed that Rozsa's sketches were indeed very detailed, though he said that David Raksin's were even more so.