To removing a room, you need either the moderator or operator role.

All rooms, permanent and temporary, can be removed by a moderator by editing the room.

In the bottom right corner of the edit form, a delete button will remove the room from the permanent room list after a removal dialogue. Any players still in the room will no longer be able to chat there when it is deleted.

Note: Temporary rooms automatically disappear when the last player leaves, though you can still remove them manually if you want to.