I have a roopie connected via coaxial to My Lyngdorf tdai-2170 amplifer. When I set volume to fixed in Roon I can not control volume from Roon or My amplifer. Worked fine with My Hegel H90. IF I set it to DSP I can control it via Roon byt not the amplifer. Set as device control the problem is the same as with fixed.
I can’t find any settings in My Lyngdorf to change it either.
It is very unlikely that you’ll hear any audible degradation by using DSP volume control in Roon but give it a try. Any degradation will be at fairly low volume levels. At normal listening volumes you’ll have plenty of bits of resolution. Still some folks prefer one way or the other. I use DSP volume with my Chord and don’t use a preamp and am quite happy with that configuration.