I owned an ARB model for a year. I used it probably 20-30 times. All my friends had one, which was nice since it really only permits a certain type of camping. Ultimately, almost all of my friends ended up selling theirs within a year. Some loved them, some didn't. Selling my RTT was one of the greatest days of my life, as I went out and bought the best backpacking gear I could find, and have been super happy ever since. I don't miss it for a second. I can still car-camp with my backpacking gear, but I couldn't backpack with my RTT.
That doesn't mean it's not for you though, i have a few friends who have them and like them. Ultimately, RTTs are a marketing phenomenon. We can all justify the reasons we "need" one (it's safer, It's cleaner, I'm off the ground so bears won't get me, etc), but don't be fooled into thinking "if only I had ______ piece of gear, I would camp more." I've found that there's no one piece of gear that will get people out more.
If all the friends you camp with don't RTTs too, you may disagree on the best places to camp, as they're not limited to places you can park.
Here's a good article a buddy of mine wrote;
https://www.rme4x4.com/showthread.php?70805-Is-a-rooftop-tent-(RTT)-for-me
Here are my opinions:
Pros:
- they look cool and get you "Kool kids" points
- it's always with you
- it's up off the ground (some people really have issues with "bugs" on the ground)
- they're fairly easy to set up (though I'm quicker with a typical REI ground tent)
- the "treehouse" factor is awesome. It's pretty fun to be up there looking over your camp.
- they get pretty dark, allowing you to sleep well past sunrise
- you can leave your bedding inside. no need to roll up sleeping bags or pads
Cons
- they're very expensive for what they are. Let me rephrase that: they're
extremely expensive for what they are. Most of them are pretty crappy tents. Think $100 big 5 tent quality. A springbar is 10x better quality than any RTT under $2k.
- interior design/pockets/layout/features were stupid. In my mind, they're designed for looks first, then functionality. Every single tent at REI has better pockets, zippers, layout, and features for 1/5 the price.
- you can only camp where your vehicle is parked. If there's a gorgeous vista or meadow 100' away, you're stuck camping on the dirt road on top of your vehicle.
- to get a level camping experience, you have to level your vehicle before setting up your tent
- it's always with you. You're carrying a 150-200lb brick on the top of your car
- lots of weight up high
- it's up off the ground. Have to pee in the middle of the night? you're now going to have to climb down a freezing cold ladder. Not a huge issue, but it turned out to be more of a pain than we imagined.
- the mattress was EXTREMELY uncomfortable. Seriously, I'd rather sleep on the dirt with no mattress. It was that bad.
- Extremely cold in snow/winter. We took it out a few times, but it had major condensation and with all the air swirling around underneath you, it never really got warm
- you're not going to want to base-camp out of it, unless it's mounted on a trailer.
- In my experience, it's not faster to set up than a ground tent
- if it rains on you with the tent deployed, you have to fold it all up away wet before you can drive. With a traditional tent, you can leave the rain fly out of its stuff sack to dry while you're driving
- when you get home, you can't easily dry your tent out without rendering your vehicle useless. Mind wouldn't fit in my garage deployed, so I'd have to wait for a non-rainy day, set it up outside, then not use my truck during the drying time. This was a HUGE reason I got rid of it.
- it's really best used for multi-day trips where you're traveling by vehicle and staying at a different spot every night.
As you can tell, for me, it's a no-go. Sure, they look cool, but for $1500-2500, I could buy the world's best backpacking sleeping pad, bag, tent, and pack, and still sleep more comfortably. And it'll all fit in a small 12"x12"x12" box, allowing me to get better mpg, more mobility, and more versatility.
Ironically, I'm now gearing up to get a pop-top installed on my van (which is pretty much a rooftop tent.) Go figure. Some people (like me) have to buy one to try it to see if it's for me.