We camp nearly every w/e from memorial day jeeping the various regional events until late october for hunting season. We've tried all the different ideas, from under the stars to canvas wall tents. We also have a Trailmaster by Venturecraft-- a packmule trailer that opens up into a nice queen sized bed. Yes, its rubicon tested but towing a trailer is sometimes not desirable, depending on conditions, etc. We still use the wall tent (love the interior wood burtning stove) for elk season but its not Jeep friendly, space wise. Thus its hauled in the full size Chevy 2500HD daily driver.
The roof mounted tents look nice, but are completely impracticable. First, the mere location way up top means u gotta climb this skinny ladder to get in/out. This can be daunting for some. Crawling out in middle of night to take a leak can be dangerous. Second, the ads always show them parked on a nice level surface. Odds are u'll not find a perfect level place to camp, thus ur tent will be off camber, adding to the entry/exit issues and besides, who can sleep w/ the tent all akimbo and not level? Third, it limits ur overhead clearance from branches, etc. and finally, it contributes a lot of weight that affects ur center of gravity, which can be dangerous. (why do wheelers add the high-lift, spare tire, gas cans etc., on top? that is a roll waiting to happen!!)
Considering all the different methods of sleeping in the rough, so to speak, next to 'under the stars' wrapped like a burrito in a sleeping bag and tarp, we have found the best of all worlds. Take a look at www.tentcot.com
Oops, that got repeated... Anyway, we found the Tentcot to be the absolute best-- one may even fold up ur bedroll inside and it takes up very little room-- it fits perfectly into the Surco aluminum roof rack.
Good luck in what u do!