Not really, there is plenty of land which is not suitable for other things. The solar power to cover all the worlds need could fit in a large desert.

And it's much cheaper and easier to install a ton of panels at once, then one and one on rooftops with varying size and design. It' also easier and cheaper to keep them clean.

But one does not rule out the other. The world should probably invest massively in both kinds of solar, since solar at rooftops with battery storage can help reduce the burden on the grid (especially when people start to need electricity to charge cars).

Large parts of both India and China are covered by deserts where you can build huge wind farm and photo-voltaic capacity without disturbing anyone. Centralised areas make more sense in terms of maintenance, so building one plant per village could make much more sense than putting everything on roof tops

Rooftop solar programs have been launched by electricity providers in a few Indian states[1][2][3]. They offer incentives like subsidy/discounts in electricity bill if a house has solar energy.

[1] https://gpcl.gujarat.gov.in/showpage.aspx?contentid=110

[2] http://bescom.org/en/solar-roof/

[3] https://en.wikipedia.org/wiki/Jawaharlal_Nehru_National_Sola...

That wouldn't really work in India, as rooftops are flat and utilized as living space.

The scale (and thus cost efficiency) is completely different. It's way easier and cheaper to build a given amount of capacity in a single massive installation than spread out across 200,000 different roofs.