The .RADIO SET command is not designed to be called by users. However, it can be. The problem is that you would need to know how Sonos internally refers to its radio stations which is not immediately apparent.
For instance, tuning KDFC is a .RADIO SET with a parameter of “s32104”. That is an internal Sonos ID. Then issue a PLAY command to start the station.
The way to get those internal Sonos IDs is not easily accessible. Today, the best way would be to use WireShark, watch what Roomie does for the station you want, and then use that ID as the IDs themselves basically never change.
What we want to do is upgrade some of these internal Sonos commands to user-friendly Sonos commands that you can just type “104.9|KDFC (Classical)” and Roomie will look it up for you when sending the command.