Th need water in the 79 degrees farenheit range. If your room stays between 77 and 80 all year, then no heater or cooler is required. If it goes below 77, which is probably does, you'll need some form of heat. People with a LOT of bettas often choose to just have a arm room, as it is more efficient.
Even with a warm room, the temp can change really wildly causing stress to the bettas. I recommend getting a heater, they're not expensive: my 25w one was about $24.95 and heats up to ten gallons.
As for lights, as long as your room isn't pitch black, they're just an accessory to let you see the tank more easily and help plants grow.
I wouldn't be happy if my bettas didn't have a heater as I'd worry about the temperature fluctuating too much.
Well done on doing the research before rushing in and buying though. Keep asking stuff until you are sure you can look after them successfully.