Do you mean the number of times a car has rolled before coming to rest? If so, my last count was five times in one crash. If you meant the total number of incidents where the car was rolled over, then my number is too high to count.
I purposely roll or crash brutally (think of a head-on collision into the AI competition at top speed) whatever car I'm driving if I get messed up and angry enough. That way it gets the anger out of my system and I restart the race and do much better afterward.
Luckily, I have yet to see any lasting negative affects on my cars as result of this anger management method.