How well does animal repellents work?

Which ones work best? I want to repellent animals (roof rats or etc.) from getting into my attic, before I close the entry. I have had several pest control companies come in, but all tell me the same thing. I have a roof rat problem, but this thing make sounds with his mouth and he's loud. He doesn't move around a lot and when he does he's loud. Since, I don't have flooring in my attic only one company actually went up there and they did not see any signs of raccoon or possum could be getting up there. If I spray a repellent first and then wait until I don't hear any noises and then close the entry will this be best?