Experience a fresh take on Rogue Party with 64 new maps! Loads of secrets, new wall models and unique layouts await.
https://store.steampowered.com/app/1106000/Rogue_Party__Map_Pack/?beta=0
If your game menu doesn't mention the DLC then you need to restart steam to get the latest patch that supports it.
You can play with people that don't have the DLC, but that will limit the maps you can visit.