We've had a double Klepper for almost 25 years, and haven't had any problems storing it assembled or disassembled for long stretches of time. If you store it assembled, be careful not to hang it from the bow and stern. Instead, use some wide webbing and support/hang it somewhere aft of the bow and forward of the stern. We borrowed a Feathercraft that had been stored assembled on its side, and over time the aluminum keel bent and the boat wants to continuously carve a turn to starboard. Be careful not to store the boat on its side. Store the boat with its air sponsons uninflated.
I think the Klepper would be a hard boat to roll because its air sponsons make the boat so wide at its sheer. Also, the spraydeck -- at least the type that came with our boat -- is not particularly waterproof when the boat is upside down. A skilled paddler with a very strong roll and hipsnap might be able to roll the boat. I've never needed to roll the Klepper -- it's rock solid in most conditions, particularly when it's loaded down with gear. The boat has a tendency to move with the swells, though it gets a little dicey surfing into a beach with a lot of gear in the bow.
We've cartopped our boat for moderate distances, using both old Yakima cradles and simple foam cradles. Be careful not to crank down on your bow and stern lines or you might harm the boat. For long trips, I pack the boat in its storage bags. The storage bags also keep the boat clean, though you should be careful of heat or dampness -- some of the parts can suffer from mildew in a moist climate. The bags also serve to catch the screws that occasionally work their way out of the wooden pieces when they get dry.
You should be able to get assembly instructions, parts lists, a repair kit and other Klepper information from Klepper America or Long Haul boats. A quick look through Sea Kayaker will identify other Klepper service centers and retailers. The boat won't require much maintenance, though you'll want to keep sand out of the boat, store it dry, and occasionally check to see if some of the wooden frame pieces need to be recoated with spar varnish. After 20 years, our spraydeck's waterproof coating began to deteriorate, and we've added a keel strip for a trip to Southeast Alaska and patched a few holes in its canvas deck. Beyond that, the boat is in good shape after a lot of wilderness use and abuse.
I've found that mixing Kleppers (at least double Kleppers) and hard boats on long trips isn't a good idea. The Kleppers are slower than most hard boats, which can lead to issues on a trip. On the other hand, the Kleppers can haul a lot of gear, especially the extra food and cooking gear that doesn't make it into the hulls of hard boats. The Kleppers are also excellent boats for introducing children to sea kayaking. I feel very confident with a pre-teen in the bow, and usually move them to the stern and the rudder control half-way through the trip.
We've used our Klepper from the Beaufort Sea to Bolinas Lagoon, and we've got a few more Alaskan river trips planned for the future. I hope you get as much enjoyment out of your Klepper as we have out of ours. In our family, it's the matriarch of a collection of boats, and still serves us well.