Thanks to all the contributions here, it's all working!
@timmo I also have a deco mesh network and decided to simply to factory reset both devices and go through the set up process with each again..... VOILA, They grouped and played in sync in WiiM so I ungrouped and regrouped them in Roon and I've got got musical bliss!
And Roon does identify each device by its playback capability. Most of my Sonos gear shows up twice, once as airplay and once as Sonosnet. One shows up as " Sonos Tested" and both WiiM's appear under Roon Ready
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