On my last TT, I had a small panel on the roof for maintaining the battery during storage. The trailer was very efficient electrical usage wise and I could generally go a 3 day weekend on the 2 group 24 batteries I had on it.
My current rig is a power hog, and I needed to install and use an inverter to use the reclining loveseat, watch tv etc as the rig is very AC oriented. I upgraded the battery bank, added a 600 watt pure sine inverter that powers all outlets. (Obviously can't run AC or microwave on it). currently there are 5 100 watt panels flat mounted on the roof. In addition, I have 100 watt panel in the garage I will install when the 5er gets back out of the shop. Controller is a bogart SC-2030 coupled with a trimetric.