There will definitly be no shutdown of the server involved when rolling back the map.
Ideally the admins will get a button that allows them to just stop persisting changes to the map made / set a older version as "boot-version" -> So that once the next round starts the specified state is loaded.
Changing the map during the current round (rolling back changes) is not needed and not a goal as antagonist action during a round should definitely have consequences, these actions just should not persist.
Regarding antagonists:
Antagonists will definitely be a thing, however there wont be persistent antagonist chars (as in the player can set the faction of his char to "syndicate" and they will always be a traitor)