@vrod29 I have tried using email address, and it fails with the exact same error as when using room name. Your advice is also proved wrong as three of the rooms work fine using the room name, but the other four don't (whether room name or email address).
Incidentally, those three rooms that work exist solely in Exchange Online, but the other four are still managed on-premise. I guess this is may relate to the problem? I'd happily move them to online-only, if there's a way to do so safely without losing all the existing bookings.
I haven't tried the Graph API as I'm not a developer, and don't intend to become one in order to administer my room bookings! I'm sure you understand.
Could you please let me know when this will be fixed? Thanks.