You didnt mention your Roku TV model # or firmware version: Settings/System/About
https://image.roku.com/c3VwcG9ydC1B/Roku-TV-User-Guide-10-0-en-US-.pdf
HDMI® mode (4K models only)
On 4K (UHD) TVs, you can independently configure each HDMI input to match the
capabilities of the connected device. From the Home screen menu, navigate to
Settings > TV inputs, and then select an enabled HDMI input. Next, select HDMI mode
and then select one of the following settings:
• Auto – Let the TV determine the best setting. Use this option unless your
HDMI® device does not correctly communicate its HDMI® version information.
• HDMI 1.4 – Configure the input for compatibility with HDMI® version 1.4, which
supports a maximum refresh rate of 30 Hz at full UHD resolution. Most HDMI®
devices will work correctly with the TV in this mode.
• HDMI 2.0 – Configure the input for compatibility with HDMI® version 2.0, which
supports a maximum refresh rate of 60 Hz at full UHD resolution. You must use
this mode to view HDR content from the device connected to this HDMI input.
However, note that many older HDMI® devices do not work correctly when the
TV’s HDMI input is set to this mode.
