Since all voice recognition is handled in the cloud by Google, and not Sonos, you may need to take this up with them. All Sonos does is pass the voice over to Google for processing. 

Thanks for the quick reply - not sure if its a google issue as we can see the Sonos Roam in the Voice Match screen from both of our google accounts.

We can fix it by removing the Sonos Roam from our list of voice match devices in Google Assistant Settings, then reloading it. But its a hassle to do that everytime we want to amend our shopping list, and it takes a while to reload the voice match onto the Sonos Roam.

Google Community forums have said this sounds like a Sonos issue.

So this problem isn’t really solved. 

Has anyone else successfully loaded 2 voice match profiles from 2 separate Google accounts onto a Sonos Roam? And got them to “stick”?

I just set up our Sonos Roam yesterday. Added Google Assistant. The Sonos Roam shows up with the rest of my Google Assistant compatible devices (including my Sonos Port and Play:3) in my Google Home and Google Assistant apps for Voice Match and Personal Results selections. However, the Sonos Roam doesn’t show up as an option for any other family members in their Google apps. Seems that the Sonos Roam only supports one Google Assistant account. Hope Sonos can address this issue. 

Ok, I figured it out. Part of our issue was that previously, we only used Nest Hubs to control our Sonos devices. I misspoke above. We controlled our Sonos Ports and Play:3 with our Nest Hubs. So our Sonos Roam was our first Sonos device with Google Assistant built-in.

The Roam was available in our respective Google Home apps. However, the Roam was listed in my Voice Match devices, but my family members couldn’t see it. What threw us off is that each of us can see all Nest Hubs available for Voice Match even if a family member is only using Voice Match on just a few of the devices. In the case of the Roam, it was displayed in the Google Home app, but it wasn’t displayed as a Voice Match option with the rest of the Nest Hub devices for anyone in the family but me.

Turns out, for each family member, it was as simple as selecting Voice Match in the Google Assistant app, then selecting “Add device with Voice Match”. And voila, the Roam was listed as an option. Family members added it and now the Roam recognizes everyone. So I can attest it does work. Good luck everyone. 

This is the solution it seems! Thank you @JasperC  !