Well, most of those gauges are more of a novelty then anything else. There are two types out there though. The one with the Jeep or truck with two separate gauges for pitch and roll. The other is a bubble meter that just shows roll. Without knowing the actual roll angle, you're really guessing. This has to take into account your CG so knowing the vehicles weight would be nice to know. Amount of lift would also come into play not to mention how soft/hard your suspension is. This is why many are installing larger tires with shorter lifts and just chopping the offending body panels for clearance.
In any case, most of the time it feels like you're going to roll but in fact you're not even close to rolling.
