I'm not sure Roddenberry was even that great when it came to ideas. I think his real talent was surrounding himself talented people.
From what I've read, as the movie series went along, Roddenberry spent less and less time dictating memos of any sort about them. In the Star Trek II production files there are a number of detailed memos from Roddenberry about the script; in the Star Trek VI production files there are none.
Well, that's probably because when Roddenberry tried to speak his mind Nick Meyer told him to go jump off a cliff.