Besides the Internet Bridge, you can have a maximum of 25 heating devices in your tado° Home.
So, in theory, if you have one tado° heating device per room, you can have up to 25 heating rooms in your Home.
For cooling systems
You can have up to 25 Smart AC Controls in your tado° Home. So, in addition to the rooms for heating, you can have a maximum of 25 rooms for cooling in your tado° Home.