Assuming the ‘Roam’ works similar to the ‘Move’ and you are away from WiFi and just connected to the speaker via Bluetooth, I think if you open the S2 Sonos App, it may show the device battery level, but I’m not near my system to actually test this.

If you go to System in the Sonos app, it should show the battery level even if you are not on WiFi and just connected to the Roam via Bluetooth.

Also, when the battery light on the Roam flashes orange, it means the battery is low (less than 15% charged).

I had already tried your suggestions as is the way ‘Move’ works.

However it doesn’t work for me with the  ‘Roam’

System is empty when Roam connected by BT

This is what I get:

Try restarting the app and make sure the app is updated.

Yes I see the same as @GuitarSuperstar. I just tested this with an iPad and the battery charge level is visible when WiFi is off and the Roam is connected by Bluetooth. 

Hey. 

You need the latest version of the app to see that battery level. I didn't updated it until today, and I was only seeing the device name while in Bluetooth bu no battery level. You also need to give the full location access (at least on Android). 

Now it works 

Thank you for your help.

I have reinstalled Sonos S2 app in my iPhone 8 and the problem continues... 
I have tested with my wife’s iPhone 11 and she has the same screens you posted me if connected in BT.

Strange. May be is a problem concerning my iPhone.