That’s on the Hegel side. Hegel apparently is working on Roon integration, but they aren’t there yet, and it’s been a while. They could then claim that the device is “Roon Ready”, and it would work transparently with Roon’s protocols, as it currently does with AirPlay. In any case, you should probably speak to Hegel or one of their representatives if you’d like better visibility there.
This all said, right here, right now, you have two options:
a) You add a “network something”, or, in RoonSpeak, an endpoint.
These can go from tens of dollars to tens of thousands of dollars depending on how comfortable you are with lego, what outputs you want and how susceptible you are to marketing claims. From the sounds of it, you want something with SPDIF out, for which there are a multitude of options.
b) You sell your Hegel and buy a replacement that’s already Roon Ready.