Bluetooth uses the 2.4ghz band and so it’s maybe worth trying a different channel on your Wifi router (if nearby) in case that’s interfering. Some phone cases/covers can interfere with a Bluetooth signal too, so if applicable,  perhaps try it without a case/cover temporarily to see if that helps. 
 

Also, last but not least, delete the Bluetooth pairing and reboot both speaker and phone and re-pair them again.

ok thanks ! But I never had any bluetooth issue with this phone in this appartment...So I suspect a malfunction with the Roam.  For sure    I will delete the Bluetooth pairing and reboot both speaker and phone and re-pair them again.will try this tonight and post feedback !

Yes - it’s just a matter of trying a few things first, if a hardware fault proves to be the outcome here, then I’m quite sure Sonos will immediately replace your unit.. but first just see what you can perhaps discover by trying the suggestions, you can go onto refer the matter to the Support Staff later, if need be.