Bitcoin transactions cannot be rolled back.
What you are talking about is ONE bitcoin exchange, and even then, they didn't 'adjust bitcoin prices'. They simply removed some of the trades that occurred during an intrusion into their database. After that, bitcoin prices were subject to market forces as usual.
Exactly. Because of the decentralized nature of Bitcoin, a mass rollback is not possible. I think the 'flash crash' has been misrepresented in various articles in the media - people don't realize that it only affected internal transactions on one exchange.