Up-sampling all formats to a DSD rate that's beyond the Dac's DSD capability

I wonder if Roon upsample to d512 with optional filters like HQPlayer ?

Whatever Roon offers has to fit in with the hardware they recommend. If their i7 Nucleus or equivalent NUC can’t do it then they won’t offer it. Roon works on the principle of strong single core performance which doesn’t suit the more complex filters HQPlayer provides.