Roon (2.0) on a NUCK ROCK does not see my Marantz SR7015 (Roon ready) as an audio device

I just installed a NUC with ROCK. The problem I have is that I also have a Marantz SR 7015 A/V (Roon ready) both connected with a switch and Roon does not detect the Marantz as an audio device. If I run Roon from a Windows 10 laptop also connected to the same switch and use the NUC-ROCK as the engine, the Marantz does appear as an audio device and I can listen to the music through it.
How do I configure Roon from the NUC only to be able to see the Marantz as an audio device and be able to listen to music with it?

A couple of things here. Marantz, like my Denon are Roon Tested not Roon Ready.

I believe Roon Tested is basically AirPlay. In Settings - Audio, Roon should have the receiver listed under the Roon Tested banner via airPlay.

Roon Ready is the device having the Roon network code embedded in the device firmware/software whatever. Then it would be listed under Roon Ready and Tested.

Can you add a view of your Settings - Audio screen?

My SR8012 shows up as an AirPlay device in Roon (Settings > Audio).

As Mike_LC mentioned, your AVR is not Roon Ready so this is all you will see unless you have a Roon bridge hooked up to one of it’s HDMI inputs.

First of all, sorry for taking so long to thank you for your help.
Indeed, my Marantz can be used via airPlay as you have answered.