Marc & Fellow Members,
Seeing that you have gone this far, I would replicate what all quality Coach manufactures do. BTW NEVER EVER use any silicone caulking on a roof. The sun will turn it into non-sealing slippery rubber, what a mess!
After cleaning down to the original surface, Apply Butyl tape sealant. Usually 1" wide by 1/8" or 3/16" thick around the perimeter of the opening. Re-install the removed component and replace the screws with the next size larger in diameter. Example" if the roof vent had #8 by 1" hex head screws, Replace with #10 by 1" screws (never any longer than original). Next apply the secondary sealant over the perimeter of the component. Overlap the edge by at least 1" on each side. I use Dicor "NON self-leveling" and apply a circular motion about the size of a Quarter as I go. Next, use a throw away paint brush and VERY slowly go over the dicor and flatten it out as you go around the component. I go in one direction and then do it again going in the other direction. Remember to go very slow. In about 15 minutes it will "level" out and look exactly like the original factory application. Coach is good to go for the next 3 years but inspect ever year for your peace of mind. I think Eric will agree. Fred