Are you speaking about Roon (what some people inappropriately call Roon Core) or are you speaking about ROCK?
Roon is core+output+control and is called Roon on the download page. It’s the whole Roon package, nothing else needed. Roon will run on either Windows, macOS or a Linux distro. It’s just another program running on your OS of choice. Probably need at least an i3.
ROCK is a linux fork written by the Roon folks and is a complete OS which can only run Roon, core+output. It must have an Intel machine. Control of ROCK must be from a phone or tablet type device.
Sounds like what you want is ROCK (not Roon or as you call it Roon core) and a NUC. Output would be thru USB, presumably the way you output from your laptop now…
If you want to build a Roon based player, you need a NUC loaded with ROCK. However you also need a silent enclosure. Akasa Plato is the one I use. An i5 or i7 is for large libraries and multiple end points with DSP applied. If you don’t need all of that an i3 is sufficient, 8gb RAM and the smallest M2 SSD you can get.
First of all, you’d REALLY struggle to pass “12.4 MHz DXD” to any DAC today
Though i also recommend the ROCK solution suggested by others, you could install the Roon Server part onto a NUC or smilar in a Windows environment also. (Or a Mac or a Linux PC for that matter) I can think of a few reasons to chose Linux or Windows over ROCK but once a ROCK server is runnning it does just what it does and no needs to tinker with it.
Roon Server gives you audio output and library in one package, you need a control though, but you mentioned a couple of options.
It has occurred to me that you won’t necessarily get the DSD rates you desire using ROCK. Not natively anyway. Check to see if your DAC is on the list of devices it is patched for. Otherwise you have to use DOP.