Just get a basic £20 USB CD drive (or stick with your external lG drive) for ripping your CDs. You’re not ripping in real time, so as long as it can read a CD sector by sector it will be fine.
If you want a more HiFi looking CD player with analog outputs, get one separately to the above, connect it directly to your amp and use it solely for that purpose, effectively bypassing Roon.
A dual purpose device (ie. RCA outputs for audio and a USB connection for connecting to a computer) is likely to add more than £20 to the cost of a traditional HiFi CD player. Likewise a device that could both play and rip a CD and store the results somewhere on your network is likely to be even more costly — as it’s basically a computer with a CD player attached.
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If you wanted to use your USB CD player as an audio source that appears in Roon then take a look at the Roon Entry Points extension (specifically the CD feature).
Annoyingly you can’t install Roon Extensions on ROCK or else the above would be a one-stop solution to both your needs ie. act as a CD player for both ripping and music playback into Roon.
What you could do however is install the Roon Extension Manager on a small Raspberry Pi (or any other computer on your network other than your NUC/ROCK) and then enable both the CD ripper extension and the Roon Entry Points extension. Your CD rips would then be sent to your Library and your CD audio would appear as a personal/private ‘radio station’ in Roon.
Lots of help on setting up and using the Roon Extension Manager and the various extension on the forums here.
Although unless you really need your CD player to appear as an audio device inside Roon (ie. you need to leverage Roon’s multi room features) and like tinkering, it’s problay simper to keep to separate devices for ripping and playing.