Phantom Gold not yet Roon Ready? [yes, they are now]

There is a no additional hardware/cost way - using UPNP.

It’s a small bit of software you can run on your Mac (the same one running Roon) that will let Roon play directly to your Phantoms.

and

Works perfectly and will play anything up to 192/24 (the max the Phantoms support) and you can control the volume using Roon.

I’m using it now.