The minimum CPU requirement for the Roon Core Server software is an i3 Intel CPU, that NAS is using an ATOM cpu, which is underpowered. It could work if you try it, just be aware it might not be up to snuff.
Roon allows you to enter your own Internet Radio stations. It does not have a find feature or tunein integration.
The other questions I cannot answer for you. Although, if you are using raspberry pis, the better option is to use Roon’s endpoint distribution system.
One thing to note is you can’t control Room as well via endpoints as with LMS pi’s and touchscreen. Currently the only way to get library support on a pi is to run it in a webrowser and have the web UI extension running on the Roon core. Roons been designed to be controlled from tablets and phones not the endpoints. It’s biggest weakness in my opinion. I switched from LMS at the beginning of the year and still miss the library abilities of jivelite having to always have your phone or tablet around to listen to music seems a little backwards to me but the interface is much better as is the recommendations. Internet radio is ok but needs work and compared to LMS iPlayer stuff for UK BBC is very limited.
I now use Ropieee on all my pis as its simple to setup and supports touchscreen for now playing and stop pause hopefully simple library stuff eventually.
OK, I will wait and see how Roon is going to develop in future.
To control Roon via my endpoints (raspberry + touchscreen) is very important for me. At least it should be possible to search and start a music track I have in my mind. AND to start / stop synchronisation with other endpoints. Only start and stop the music is not enough control for me. I do not like to have my phone or tablet all the time around me in order to listen to music.