To protect the RV roof from sun, clean it regularly, seal the roof surfaces using silicone based sealer and cover the RV to limit the sun exposure. The damage sun can cause to your RVs roof can be higher if it is exposed to high UV radiations for prolonged time. Unlike winter or snow, the damage sun can cause may not be visible to you quickly. But, it can be bad in long term. And therefore, tackling it in time is the best option you have.