I do not think a swaybar keeps a vehicle from actually rolling. I think the intent is to help you retain control of the truck so you do not lose control.

The danger would be over/under steering if you had to swerve, or make some other type of emergency manuver and losing control of your truck. Once you lose directional control of your vehicle on the hiway it is all a crapshoot. You might roll, eat a semi, or just "spin out" on the shoulder.

I think the Jimmy took care of the out of control part in the above example, a sway bar was not going to help much if at all. I have had a simliar incident happen at high speed in a Samurai and did not roll either, we all get lucky from time to time.

JonH