False. Ethereum did not roll back the attacker's gains, instead, there was a transaction made in the fork that moved the ETH out of TheDAO into a new contract where the ETH was returned to its owners. (An "irregular state change", or a "roll-forward" rather than back).

At no point was the ETH in the attacker's hands. Most of the ETH was trapped in a stalemate between the attackers (white-hats and black-hats), the remainder was time-locked under the Dao's control until the fork.

Also, the complete history of TheDAO is still on the mainchain and is being replayed and re-validated each time you do a fresh sync.