Hmm, well you really have only two options the way I see it.

1) Move out and find a new place to live, either on your own or with pot-friendly people.

2) Turn them into stoners. It's not as hard as you might think. Explain to them that there's no evidence it kills brain cells or anything like that (unlike beer), and that it's actually safer to smoke than tobacco. With enough peer pressure you can probably get them to take a few tokes off a joint, and then...well, once you go green you never go back.