Hello,
From the User Guide > Audio > Sonos support page;
“Sonos Zones can be “grouped” to play the same content, but Sonos zones can only be grouped with other Sonos zones.”
As this page was posted in 2017, am wondering if this situation has changed in any way… would love to group a few Sonos pieces in a broader “house” zone but no luck… any workarounds?
Cheers
Unfortunately, the answer is no. I’ve tried after every major Roon update to synchronise Sonos and non-Sonos groups with no success. As far as I know, there are no workarounds.
BTW, are you the same Wdw from Devialet Chat? If so, Hi! 
You can’t sync different protocols as they all use different methods to sync the clocks to keep them in sync. You can use Airplay with Sonos and sync with other airplay buy thats it.
From the knowledge base and suspect this is due to the Roon architecture…
Hello Axel. yes, one and the same! Best, Warren