fan and roof repair

while preparing roof for fantastic fan, I noticed in the corner it was torn. when they installed the wood, they did not screw down or nail this corner down. lucky it was sealed well no leaks.
HOW to repair?
could I lift up the rubber and put in some screws, then put eternabond all the way around. then install fan on top of eternabond and seal.

man the cleaner sure did a great job. I did use a heat gun to help loosen the sealant. took about 1 1/2 hrs just to clean.
sorry the first 2 picks are fuzzy.
thanks. also found out getting older is no fun