Honestly, I'm still not sure exactly what happened and plan to go back and look at the scene again during daylight. Obviously, right after the accident, we were more worried about getting help and making sure other cars didn't hit the car again. There is a ditch right at the edge of the road, so I'm not sure what part it played in causing the car to roll. The left corner of the windshield took all the damage during the roll, and it did end up right side up. The rear end damage someone else questioned about is from a tree that the car "backed" into after the roll.

As bad as it was, this confirmed to me that when BMW makes claims about safety, they mean it. I feel even more confident about the safety of my 2001 325Ci after this.