Your best bet is going to be sealing up any openings where they can get in. Buy a screen for your attic vents if you think that's where they are getting in, etc. You might also trim back any branches that are rubbing or close to rubbing on your roof--that will help the roof last longer, and keep out all sorts of pests (i.e. ants). That's the best I can tell you, sorry I'm not more help. If you post under General Tech in the Do-It-Yourself forum, JohnWill or someone might have better advice for you.