Dirac FAQ says this ....
4.1. What sample rates does DAP support?
The DAP supports any sample rates up to 192 kHz which have been designed into the Dirac Live® filters. The sample rates designed into the Dirac Live® filters are selected by the user from the rates supported by the sound device used in the DLCT. However, to fully support a certain sample rate, then each of the blocks in the process line below have to support that rate. Note that the operating system can be configured to a different sample rate than the media player, making the operating system re-sample the data to its configured sample rate. This re-sampling can be detrimental to the audio quality! Try setting the operating system to use the original source sampling rate. User control over sampling rate is not possible in Windows XP.
That reads like it convolves at the native rate (up to 192k), i.e. Dirac does not reseample.
I imagine Roon's upsampling is high quality though, definitely compared to Win10/macOS.