We had a 11 ft. inflatable but it turned out to be impractical for use with the camper. First it was heavy and bulky and we kept it in the rear of the cab of the truck along with the thwarts and a motor (either and outboard and fuel cannister or a trolling motor with a deep cycle battery. We also tried a Porta-bote and I attached side brackets where the camper jacks are mounted and this worked well for transporting the boat but still had the outboard in the cab.
Third approach has been to use kayaks on a kayak trailer and this works the best for us. I did not want to pull a 70 lb. kayak up on the roof and the kayaks would block our skylights and air vents with our 845 camper. With the trailer I can rig the two kayaks and then back them to the launch area and have them in the water in minutes. Overall the logistics work better end to end with the kayaks and the trailer.
Another option I considered was the special RV racks I found at www.rvkayakrack.com. They make racks that attach to the hitch or a hitch extension and hold two to four kayaks vertically (limited to a 11' long kayak) and can also hold two bicycles. One type has a swing away design so it works where the camper has a rear entry. This one is very expensive but the racks for a RV with side entry are only $1300 which is about what a basic kayak trailer costs.