I use Dicor products, these are approve for rubber roofs. When Keystone had a recall out on the lap sealant failing on some 2010 models. I contacted my dealer about the recall and asked if I could review and repair if required. Since I was in another state at the time. Dealer sent me two tubes of Dicor sealant for the roof to re-seam the roof if required. These were waiting for me at home when we got back.
Here is a link to the camping world page for Dicor products.
Search - lap sealant - Camping World