Tanner since you did not allow folks to respond to your post about setting up the display on Roku I had to create a new post to address the issue.
I have a very new 2019 Vizio and a brand new Ultra 4661 passing through a Sony STRDN-1080 which is capable of seeing anything your device can throw at it.
VIZIO P-Series® Quantum 65” Class (64.50 Diag.) 4K HDR Smart TV | PQ65-F1
When I select auto detect and go to find an available show on Amazon for example (Hanna 4K UHD) my display returns that show in 1080P.
If I go into settings and select 4K HDR @ 60Hz Roku gives me a green check on all three test. I return to amazon to watch the same show (Hanna 4K UHD) the display immediately recognizes 2160P HDR10 content.
Please explain how your Roku auto detect is selecting the highest resolution available in this circumstance. There is clearly something going on here and from another post I created your Auto Detect keeps taking over my setup after I shut the system down. I don't want to have to reset the display setting every time I turn my TV on and since your product is recognizing all of the capabilities of your highest display setting why it is returning to Auto Detect after power down?