Having the same issue. Had been using a Roku Ultra (2016) with an LG OLED65C6 with mostly no issues. However, the audio was not behaving correctly in all situations (video was fine).
Decided it was time to upgrade to the Roku Ultra 2022 and that's when the video issues started. Tried three different certified HDMI cables thinking that might be the problem, but same issue. It will only auto detect 1080p Dolby Vision. TV supports both 4K HDR and 4K Dolby Vision. Sound works great and passes Dolby Atmos correctly.
Auto will always run in 1080P DV and if I force it to anything other than that it will work while watching and then after I come back it will revert to the auto setting which only displays 1080p.
Found the secret HDMI Menu and it confirms that everything is being detected correctly from the source to the display as it shows compatibility with the higher resolutions.
EDIT:
Secret Menu: (5X Home, Down, Left, 3X Up)
Disabling Automatic Recovery fixed my issue with this. After disabling and setting manual 4k resolution it stays that way and does not revert on it's own.
https://photos.app.goo.gl/qxo6RsGY2S2thRKK8
