Room temp is great for heat. Snails have both sexes and remain impregnated for a long time. So chances are they are pregnant by the time you get them. Normally you get excess snails in your tank if there is excess food for them. This could be extra fish food, lots of tastey algea or even some munchy plants. From what I have seen the eggs can stay unhatched for a short period of time or a long period of time. I had a back that didn't hatch for a month, but some are ready in a week. (Ram's Horn). A floating piece of lettuce is great as the snails will attach themselves to it and then you can just easily pluck it out to either throw away or place into a tank with snail eaters.