Most places including the Superlift ORP in Hot Springs, AR require any SUV to have a fully enclosed cab and/or rollbar protection. In other words, either have a factory hardtop or half-cab top in place or you need a rollcage. A few parks I've been to flat out require you to have a hradtop in place, even with a rollcage. That's often to keep all of your stuff from scattering eveywhere should you roll over, but does add some strength to the body.
I have a 10-point rollcage inside the 84 fullsize Bronco, but prefer the "family-style" cage for the early Broncos, especially if you want any passengers back there. I took out my back seat so only one person can ride with me, and the rear kickers come down right where the back seat would normally be. I strongly suggest tieing the cage to the frame for safety, too.