Can someone explain how an ETH rollback would work

I don't understand how a rollback can be accomplished. Please explain if I'm missing something.

For miners it would mean any blocks that they find would just disappear back to the moment of the rollback? If so miners would not want to adopt the new code or at the least should stop mining now (waste of electricity).

All transactions back to the moment of the rollback would just disappear? If so how could that be accomplished? If a user transfers all their ETH to an exchange now sells it for bitcoin, transfers bitcoin out of exchange now, after the roll back doesn't he have his ETH back plus the bitcoin? Doesn't the buyer lose all their ETH?

Seems like a rollback just does not make sense. Is considering one just marketing so those in the know can get their money out?