It depends upon where you travel in the Jeep. Chances are that your Wrangler is already heavier and with a higher center of gravity due to a lift and bigger tires. In that case, the addition of a rack and tent above the roof makes it lots worse. Two types of terrain that Wranglers with roof racks need to avoid are paved roads (which have higher travel speeds) and uneven offroad terrain. These are where the chance of a rollover rises to a dangerous level.
For most Jeeps in most places, pulling a trailer with a rooftop tent is the better option. A trailer costs more is about the only drawback, and a trailer also requires that you install a tow-rated rear bumper. But the risk of rollover on paved roads is much reduced, and offroad, you can roll the trailer and not the Jeep, if you use a multi-axis coupler.
1967 Kaiser Commando
2001 Grand Cherokee WJ
2003 Rubicon TJ