LOL! So, I figured out a way to get the Roku unattached, simple hookup on my AVR. Downloaded the Tidal app. Nada....same issues. When I open up the audio choices via my Denon, there is NO mention of Atmos. Also, multi-channel in is missing (sort of the auto setting on my AVR for all sources). Again, it defaults to Dolby Surround (all 5.1.4 speakers are functioning though) and this is simply an upmix and sounds dreadful. I can toggle down to Auro-3D, which oddly sounds way better...but clearly not Atmos.
Off comes the Roku. At least I know I'm not going to buy another Roku...for Tidal that is. Another oddity with the Roku, the settings for Tidal...have no settings. I click on it and it opens a window that says "log out". Bizarre. Settings on the desktop app literally have multiple settings. Why are they so different?