So, it's 65-95 degrees F on average... As high as 104, and as low as 40 sometimes. I assume you'll have the tank inside, so at least they will be more stable. Let's assume that you'll keep it close to the average.
Still not sure why you want the fish to be a vegetarian.. You want to feed it plants? Lots of fish can be fed vegetables, but plants might be a problem.
If your water is around 7.0, you could try Bettas. Your given temps are a bit high for them, but they're native to India.. They should be able to handle it as long as the temps don't fluctuate wildly. A sorority would be relatively peaceful and easy to keep. They nibble on veggies, but not sure whether they'd eat aquatic plants. A commercial fish food would be best for them, and all of the others I mention. (in addition to the veggies)
Below 7.0, then gouramis and rasboras would be best, with perhaps loaches after the tank is established.
If your water is more basic (7.0-7.6, with a high Kh) then your best bet would probably be Danios, rosy barbs, gouramis. They are all native to India. You could also try livebearers instead.
If your PH is above 7.6, then perhaps you could try one of the african cichlids...
Research up on the nitrogen cycle... Then add a 1-2 fish that I listed first for each ph. Add 1-2 more every 6-8 weeks until the tank is stocked. Danios and Rasboras need to be in groups of at least 6.