In the topic [Roon and the Auralic Aries][1] you’ll see that Roon is still developing integration to your Auralic Aries. Which is why Roon doesn’t see it yet.
At this moment you could hook your windows 8.1 PC directly via USB to your TDAI-2170, after which it will see it. If they are too far apart for a USB cable (and you can’t move the PC) an option might be to use another PC temporarily as a Roon remote, connected to the Lyngdorf.
The other alternative of course is to wait till the Aries support is released.
[1]: Roon and the Auralic Aries