I've done, and still do, a lot of tent camping as well as just roll-out-the-bag-on-the-ground camping from my motorcycle. And, I have my camper. The main difference between a camper and a tent is; I can live in my camper, I can only sleep in my tent. Long as weather is mild, not a big deal, but still...
Personally, I see that roof top tent as an accident just waiting to happen. Sooner or later, you are going to fall. It would be impossible to move your stuff into the roof top safely so both hands are on the ladder. If a foot or leg gets wrapped up in the ladder or you hit the ground wrong, well then, there you are; all alone way out there where no one else is just 'cause you can, with a busted leg or worse.