Any room can be easily deleted. Just pick the room you wish to delete by tapping in the centre of it like that:

Use the Bin icon or press Backspace button (if you’re using the Web platform on your computer) to delete the room.

If you're using another platform (iOS, macOS, Android, Windows) you will have an option Delete after you pick the room.

All objects attached to that room will remain untouched. If you want to delete them as well, you’ll need to pick each of those and repeat the action we’ve just made.