I wash my roof/TT twice a yea. (We wax the tt twice a year as well). Washing the roof helps decrease black streaks down the sides. As others have stated it is part of the recommended maintenance. we too use this time to inspect the roof. I use Awesome and it does a great job. We also hit the roof with an rv roof conditioner when we wash it (available at Walmart or camping world). I have yet to have issue with minor twigs etc. I would think repeated scraping could be a problem or a large branch could cause issue but that is what insurance is for.
