I am not familiar with Lumin but a quick search is saying that the whole Lumin line does not support multi-channel. Maybe there have been some recent changes.
In your original post you say you want to stream dolby to up to 5 speakers I assume via roon, so I am a bit confused now. Your end-point will need to support multi-channel and report that back to roon.
There is probably a more up to date thread.