Both Sonos Radio and Spotify have free versions to use. Try both of them and see which one you like the best. Or better yet, use both. You are not limited to using one music service.
I’m not sure why you would describe S2 as a “service”. S2 is the software the system is running on, controlled by the Sonos app (systems on S1 software are controlled by the S1 app). You can use the Sonos app when the Roam is connected to your wifi, but not when you connect with it by bluetooth.
In the Sonos app you can add music services (like Spotify), and use preinstalled services like TuneIn. You can also play to the Roam directly from the Spotify app.
OK, so I understand that about S2. Why do I need S1 on my mobile device if I have a S2 speaker?
Thanks.
If you do not have S1 speakers, you don’t.