Ditto to ignoring the advice that the body is good enough.
Luckily I was not in my Rubicon when it decided to pop out of park and roll away. It left the road at a nice slow speed and the first roll was nice and soft. The second roll was a bit harder. Then it came up on it's tires and shot over a 10 foot drop, ripping out a small tree as it landed. Came down on it's tires and then shot another 10 foot drop, went a bit further and went over a 15 fot drop. Then it finally hit a tree large enough to stop it, but it wasn't a square hit, it was a clip on the front right corner so the jeep twisted and summer-saulted 5 times before coming to rest on it's side 90 feet from the tree.
While the body was beat to crap, my upgraded roll cage, rock rails, and bumpers protected the passenger area and the engine bay. If the frame hadn't folded and punctured the oil filter when it hit the tree the Jeep would have run, and I was able to use my own winch to help with the recovery. Passengers would have been shaken very badly, but would have survived. A stock TJ would not have survived and a Cherokee would not have either. Both vehicles would have crushed the sides and roof far enough to injure passengers.
I do not have a cage in my XJ yet, but believe me, it's a priority.