Rollback Set

A Rollback Set is used to create older ROM sets for previous versions of MAME.

That's needed to run on old hardware, or to play a game that does not run in the latest version of MAME.

To create a Rollback Set you need:
 * the latest MAME set
 * the latest Rollback torrent
 * the DAT File of the old set you are planning to make

With the above you can rebuild it yourself using clrmamepro or RomVault.