It is usually set to auto, but if you want to change the video resolution on a Roku device, you can go to Settings and then Display Type. You can also manually configure the display type to detect the best resolution for your TV.
Press the Home button on your Roku remote
Select Settings
Select Display Type
Select one of the available display types
Press OK on your remote
When an image is shown, select Yes, I can see it and press OK on your remote.
For a Roku TV, you can go to Picture Settings and select Picture Size. It is also normally set to auto.
Open an input, like HDMI, live TV, or a streaming app
Play a video
Press the Option button on your Roku remote
Select Picture Settings
Select Customize Picture
Scroll down and select Picture Size
Select Auto or Direct
Select Apply Settings to all Inputs to apply the picture size to all inputs
