In case anyone is interested in this, Roon now works feeding Sonos speakers as of Ver 1.3, released today. (Not seeing 1.3 there yet at download page, but will likely be there tomorrow). I suspect this is a good option for those with larger than ~65k music libraries. The Roon integrated database of information is quite nice as well. In any case, I have no financial interest in Roon, just letting other SONOS users know about the recent change.
"With the 1.3 update, Roon now streams to Sonos devices! This means all the users in a home – with one app and one music collection – can play music to Sonos, Airplay, Squeezebox, Sooloos, and any of over 50 Roon Ready devices available today. "