Have you tried reserving an ip-adress for the Roam?

As above.  I have added a reserved IP address for all my Sonos speakers, including the Roam and Move.  No issues since, but then neither did i have before.  It is very easy to do too on the Eero app.  You can also name the devices for easy identification.

Also see if turning off the WiFi battery saving option makes a difference.

First, I made a small discovery. My Sonos Roam would drop off the network, and taking it in and out of sleep mode didn’t change that. I discovered though that if I power the Sonos Roam off and power it back on that it rejoins the network.

I went into my Eero app and assigned a static IP address to my roam.

I also turned off both battery saving options on my Sonos Roam.

It usually takes around three days before it drops off of the network, so it’ll take me a while before I’m convinced it’s working, but at least I’m more optimistic than I’ve been in a while! thanks for the tips, and I’ll keep my fingers crossed!

It’s been six days since I gave my Sonos roam a static IP address and turned off the battery saving options, and it hasn’t dropped off of the network since! I think my problme is solved, so thanks for the help!

I spoke too soon. My Sonos Roam fell of my network twice today. I powered it off and restarted it to get it back on the network. I’ll keep using this as a work around, unless there are any other ideas to try.

I'm having the same issue on a Deco M9 network (also mesh). Hours on the phone with Sonos support and even a replacement unit didn't help. Were you able to find a solution?

No I wasn’t. Like I said, I just power off my Roam and restart it to get it back on the network. Sometimes this will last for days and other times it just takes a few hours.

I have to say my system has been stable all the time. Yes this may not help but it does show it can be achieved. 
I have 3 Eero pro 6s and over 10 Sonos devices with a mix of wired, wireless and Sonosnet. No Boost. My eero Network is the only WiFi I have and my Virgin router has been set to modem mode so all my ip settings are managed with the eero set up.

The Roams shut down on full battery saving and start up without issue.