Hi,
If your rooms can be booked individually, then you have to setup a listing for each room. Each room will have seperate calender, so future guest can see the avialibility of each room. You need to do some tuning anyway, as the sleeping facilities (what kind of beds etc..) are not mentioned now. In the description (or even title) you can indicate they are in the same building. Guest will notice also same pictures of public spaces will show up (and make it even more clear to them by adding a picture of the building also)
Best, Emiel