On a slightly related note, is there an easy way to measure if a specific digital chain is bit-perfect? My chain is DLNA server (FLAC files) -> BubbleUPnP application -> Chromecast Audio (TOSLINK output), and I would love to perform some testing.
As Amir said, its not easy. A while ago, for an entirely different reason, I was using an ADC to record to file and then compare the files using a freeware tool (http://www.libinst.com/Audio DiffMaker.htm) which back then was controversial for reasons I can't remember. Introducing the analog domain into the chain results in non-deterministic output which results in uncertainty.
A lot of times, unless its open source and you can understand the code, it is a matter of trust. I've communicated with Roon folks a while ago and being a software engineer myself, I was able to gauge their design & coding principles to some extent. That led me to trust them.
I don't know what the DCS renderer does, but it could have bugs and or features that change the incoming streaming somehow. Roon may have bugs too. I would prefer Roon because I trust them to do the right thing.