From experience with extractor fans is where to place the vent. I have learned very slowly that penetrating the roof is not the best idea.
When I had a new roof installed I should have had all roof top vents covered over except the plumbing vent pipes. Even those can go in a much better spot.
Gable ends and soffits are perfect for a vent and eliminate the possibility of roof leaks from roof top vents.
My point is do not vent out the roof if at all possible. There are other places that are much better and there is little concern for water intrusion.