That's an adorable pony rolling in an arena. It's also an adorable pony rolling in my PS of Sweden bridle.
I'd pulled off the reins for lunging and she clearly wanted to roll so after I got rid of the rest of the lunging equipment I let her go. It was only after she rolled to the other side that I realized that allowing her to roll in a bridle (especially this one) probably wasn't a good idea. I was able to get the sand off and it didn't get scratched but I certainly won't be doing that again.