I'd start by checking what axles are on the camper...probably 4000 lb axles (should be a sticker on the front, left corner). If they are 4000 lb axles, you need tires with a load rating the exceeds that. The 205/75R15 C is rated at 1820 lbs. I'm betting the OEM tire was 225/75R15 C rated at 2150 lb...that's the OEM Tire on a 2010 Rockwood 5ver. If you're buying a new set, I go with 225/75R15 D rated at 2540 lb.
Nights camped in 2013 - 55, 2014 - 105, 2015 - 63