Linux and DSD can be tricky.
First, make sure that the DAC can work under Linux at all, some require Windows drivers to function (not talking about DSD yet).
Next, Linux like MAC OS can do DOP DSD, in which the DSD is encapsulated in PCM. The DAC needs to be able to support DOP, not all do. Now this IS DSD not PCM. The extra wrapping will eat up some resolution, so DOP resolution maximums will always be one step down from the native max resolution. Meaning if a DAC can do native 256 DSD, then the max DOP is 128.
Finally, if you want to get Native DSD, then it gets trickier since each DAC needs to be individually supported in each and every different Linux build. So you need to verify that the DAC AND the Linux version (Rock in this case) will work together natively.
Others may chime in with their own DACs which work natively with ROCK, and that would be a good start in making your DAC short list.
Otherwise other options are to separate the DAC from ROCK with something like a microRendu, who provides a list of DACs for which native DSD support has been added. Another, is to use a 2nd computer running Windows running the DAC drivers and Roon Endpoint software (not the core). Or, just run Windows and the DAC devices drivers on the Core NUC.