Based upon a previous discussion: 5.1 to 7.1 not supported for FLAC/WAV?
Roon doesn’t do multichannel up-mixing:
Can you elaborate what makes you believe Roon is performing up-mixing, especially for the usually performance hungry to process DSD format but not the easy to compute PCM format? Can you provide screenshots of Roon’s signal path for relevant cases please? Do you use any special DSP filters (convolution)?
Also what is the origin of those DSD files (official purchase, CD/DVD RIP)? Did you ever look inside the file container to check the format (and channels) of what’s actually inside?