Sonos roam has been a nightmare for us as a custom installer. I chronic issue with not showing up in the app. 
This device has cost me hundreds of dollars in service calls to our clients. 
the device is used and plugged in with out ever being removed from the room. And it constantly falls off the app.
Frustrating is a nice way to put it. PITA is better. 
I have this same set up in my own home and have had nothing but problems exactly as my customers have with it falling off the app. 
We have done the router reset so many times and yes it comes back with in a few days it’s gone again. Sonos seems to have gone down hill since going Public. We are over this product. I will not let customers purchase it with any support from us any longer because of these issues.