This isn't recommended... there are going to be issues.
First off, your peers don't contain the game state data by default, when they reconnect to a second "backup" room they won't have all of the game state information. They would need to get it from the host... which disconnected unexpectedly in the first place.
There isn't a way to redirect new joining players to a second room from the first.
If you manage to preserve the game state data on each peer client side, then it would make more sense for everyone to rejoin the same room with a new host, and try to match up the player aliases with their new peerids and reassign objects (this is going to be a major headache).
Again, while it is possible to do some sort of host migration, it is going to have problems and probably end up being way more effort than it is worth. It makes much more sense to use a proper dedicated host or use a third party backend service.