Roddenberry specifically wasn't needed, Rick Berman was able to learn from his vision and maintain it. After Roddenberry died, Berman was able to maintain TNG, DS9, Voyager, and Enterprise all with the Star Trek ideals that Roddenberry always fought to maintain when he was alive. Even as Deep Space Nine and Enterprise had to seemingly throw the ideals out the window temporarily, with the Dominion and Xindi arcs, just to better demonstrate why they were so badly needed in the first place.

Unfortunately, we don't have a Rick Berman, or anyone else that maintains the same ideals, at the helm anymore.