Yes, with a T2 you can play DSD512 from Roon via network because it’s Roon Ready. T2 does not support USB input. (However, T2 can optionally output to another USB DAC.)
As for the DAC you originally asked, I worked with a customer years ago to get Linux native DSD working but not successful. At that time he claimed he had the latest XMOS firmware, but the USB VID PID was not expected, and even if I made a Lumin U1 custom firmware for that Linux USB native DSD output to that USB VID PID it still did not work. Anyway, that a was a few years ago. If you choose to purchase it, I suggest you check with the manufacturer first.
Robert’s photo above only proved his microRendu can output Linux USB native DSD to ultraDigital (not the DAC), and proved the DAC supported DSD256 via i2s (not Linux USB). That photo does not confirm or deny Linux USB native DSD output to the DAC. If he gets bit perfect DSD256 playing without the ultraDigital in between the microRendu and the DAC, then it is proved that a recent enough hardware / firmware version of the DAC supports Linux native DSD as you need.