Another decent "big idea" was Andromeda. But somebody else had to take the concept and develop it into reality.
Actually
Andromeda was retooled from an idea Roddenberry
did execute twice, as the pilot movies
Genesis II and
Planet Earth. Majel Roddenberry's producing partners and showrunner Robert Hewitt Wolfe, with input from Kevin Sorbo, took the
Genesis II/Dylan Hunt concept, retooled it as a space show (at Sorbo's request), threw in the idea of an intelligent starship from an unsold Roddenberry premise called
Starship (which I believe was the original source of the Matt Jefferies "ringship" design), and mixed it together with some of Wolfe's ideas for a hypothetical post-apocalyptic
Star Trek series he'd mused about.
A better example would be Tribune's previous Roddenberry-inspired series,
Earth: Final Conflict. That was based on an actual Roddenberry pilot script called
Battleground Earth, and in fact its pilot episode gave Roddenberry sole writing credit, even though the script and concept were revised by E:FC's developer Richard C. Okie. In GR's original version, the aliens were more malevolent, which was too similar to
V, so Okie adjusted things to make their motives more ambiguous.
As for problem solving, he was certainly very good at finding the right people to make things happen. I once knew a man such as him. Others revered him as a "genius" because of his amazing ideas, but somehow they'd never fully develop well. He'd find great talent to enact his ideas, but then he'd muddy the waters, stifling the direction of success, take credit for other people's ideas, but then just as soon disown them if they didn't make it. Just like Gene.
True -- GR did gather good people around him, at least in his prime. Gene Coon, Bob Justman, D. C. Fontana, Matt Jefferies, Bill Theiss, Fred Phillips, etc. -- it was the whole team that made TOS great (including the cast and the freelance writers too). And he had a good team for TNG too -- Justman, Fontana, David Gerrold -- but unfortunately by that point his judgment wasn't as great and he'd gathered a couple of other people around him (Richard Arnold, Leonard Maizlish) who were, shall we say, not team players and ended up driving the others away. (I often wonder what TNG would've been like if it had been Justman, Fontana, and Gerrold who stayed and the others who left, instead of the reverse.)