Got a response from Devialet support today:
“…Devialet Phantom is NOT Roon-ready yet so Roon Raat is not an option at this stage.”
This is of course not an acceptable response so I’ve sent a reply/new request.
Another thing is that on my reply I Cc:'ed Quentin Sannié who used to be CEO and got a bounce from Devialet’s mail server. I didn’t know that he’d quit so maybe it is false alarm. He may simply have changed to a different mail alias…