Bettas come from the hot waters of thailand. These rice paddies can get very hot due to the shallowness of the water. Bettas have a wide tolerance range when it comes to water temperature. Their have been reports of the bettas lasting the night in peoples cars.
Bettas can also handle warm temps such as 90*F. Room temperature is just fine for bettas, but remember the basics. The warmer the water, the more active the betta is, and the faster the metaoblism rate is. Heaters come in a wide range of wattage and sizes. So there are a few out there good for ten gallons or smaller. While it is a good thing to have a heater, it isnt really required when it comes to bettas.
Filters are not required, but like heaters they are recommended. Filters are great because they help keep the aquarium water in the best condition for your fish. Long fin male bettas however, have special needs. The current that power filters create isnt all that great for bettas. Their long fins often get stuck in the filter intake and cause the fish to have swimming problems. Gentle filters such as sponge filters are best for bettas. These filters pick up solid waste in the water and also provide some chemical/ biological filteration. Being air powered these filters can be adjusted to fit your bettas needs. They dont pose any threat to bettas and would be a good addition to any betta tank.