Yes…
I also thought it was not possible, but I’ve just tried it on my ND5 XS2 (similar firmware) and I can control volume from Roon. Select ‘variable’ from the Naim app, then shutdown and unplug the Naim, count to ten, plug it back in and it should be good.
I suspect the NDX2 is doing volume control at 32bit resolution, so although theoretically it’s compromising sound quality I wouldn’t worry about it. If you can hear a difference, switch it back!