Bought 2014 Keystone Alpine 3600 RS new.Sat in lot for 3 years. Maintained and kept up. Wife retires. Tow rig to Arizona via Santa Fe NM. Bought cover for it. Upon covering, noticed separation of roof...
How big is the bubble? From what you described there is already a 1/4 gap or so from the front cap to the rubber roof, so I would lift the rubber look for any rotted roof substrate. If the roof is dry and sound I would glue it back down and attach the front of the rubber roof with a 4 in wide strip of eternabond tape or eq to cover the front cap. Once you prepare the rubber and FG cap it will hold the roof in place and keep it from peeling back.