Welcome to the Roku Community, @JAGKU!
Thanks for reaching out. We'd like to provide further information about this.
Kindly ensure you've plugged in your PS5 directly on HDMI ports 1 or 2, as these are the only ports that support HDMI 2.1. The HDMI 3 and 4 are not supported.
In addition, what specific cable are you using?
We'll be looking forward to your update so we can take a closer look.
Best regards,
Carly
Carly Y.
Roku Community Moderator