This is a bit of an end around, but I am actually using a single HEOS 5 with my iMac desktop. I am cabled USB out to a Cambridge Audio DAC Magic (for my headphone listening) and the analog out of the DAC is hard wired to a single HEOS 5. You might be able to get it to function through the headphones out jack as well. I can also zone a second set of desktop powered speakers through Roon which play simultaneously. The music is accessed through the Heos 5 Aux in and you have to press the “play arrow” for it to play. Unfortunately, you have to have a tablet or phone handy since there isn’t a desktop app for Heos at the present. Hope that helps.
Most of the companies I mention Roon to don’t want to discuss future plans. Just went through this with Deezer & Bluesound.