Stash Live snapshots are stored as separate backup entries. You can find all recent snapshots via wp-dashboard ► BackupBuddy ► Stash Live.
When hovering over the snapshot you wish to rollback to, the option to "Copy to Local" will be displayed.
Click the "Copy to Local" option, and the snapshot will be transferred to the BackupBuddy "Backups" section, from where you can restore the snapshot (i.e. perform a so-called "database rollback") just as you would with any other backup restoration.
Once you click "Restore" you will see the file(s) begin to process. You can navigate away from the screen while the restore is happening.