We have a couple in the roof as well, I can hear their little feet sprinting across the ceiling at night. I've been using peanut butter, a bucket with water, a rod going through a bottle to act like a log on water.. no success yet, however, we had one in the house and I managed to corner it in the bathroom and caught it through sheer determination and luck.
The only reason I haven't used poison because I don't want them to die in the roof space.