The most realistic residential installation I've seen was firmly on the ground at a ~2 acre property. The panels were much larger and heavier (i.e., capable) than what you'd typically find on a roof. It's much easier to build and maintain a solar array when you don't need a ladder/crane to move things around.
I think that it's great that we want to participate in making things better, but not every situation makes sense. When you factor in all of the downstream consequences of sub-optimal, fly-by-night installs, it starts to look like a net negative on the environment. I'm not trying to claim that all rooftop solar projects are bad, but most of the residential ones I've seen make absolutely zero economic sense.
Large scale wind and solar projects are the best way forward. You get so much more bang for buck. I'd consider investing in these projects or their upstream suppliers and owners if you want to get involved financially in making the environment a better place.