I haven’t contact support yet. I’ll contact support tomorrow morning, first thing.
Have you contacted Sonos directly, as suggested in the post directly before yours?
I have experienced exactly the same problem. The usb-c cable started melting and smoking… Crazy! The plastic was dripping on my finger and the Roam was Hot. Luckily I was working home and could unplug the device. But this doesn't feel right...
Don’t attempt to charge the unit again and contact SONOS support. I suspect that this is an issue with the charging cable, but of course I cannot know this for certain from my seat.
If you can, take a good picture of the unit showing the USB connection to ROAM and the cable damage.
We don’t know if there is any possibility of a battery incident. By now the unit should be cool to the touch. Until we know more about the failure I recommend stowing the unit such that, if it overheats, it will not damage anything near it.
And yes it was plugged in with the factory Sonos USBC cable in a GFCI outlet no less.