Never rolled it, thankfully. Had the front wheels come up awfully high a few times... we were baling high-moisture alfalfa, so the bales were heavy. I was using a Massey Ferguson 250--the smallest tractor on our farm, with no roll bars.
We used bale forks that attached to the three point hitch of the tractor. Looked kind of like a curved forklift. Never, never try to pick one up with your front end facing uphill.... over you go! Which was always lots of fun when the bale rolled down the hill and came to rest on the stream bank...