Hi Adam there is enough information here in the forums and elsewhere to get you going on a Pi based streamer and with a very low level of technical skills required.
It is worth looking at some of the forum posts and reading up a little, but either USB or Toslink would work well I imagine (could not tell if that is a SPDIF on the back as well).
Have a look at a post like this to start (but there are plenty)
I I use HiFiBerry gear (low cost and decent quality) Title of Page
Allo is another respected brand Title of Page
I imagine anything else is 3 or 4 times the price and the effort is very low
Other than that look at the partners page here What does Roon work with?
Regards
Mike