@Angelz
On a Roku device, the ability to set the desired resolution is under Settings/Display.
However, I believe when using a RokuTV, any ability may be limited to doing it in a channel/app setting as you described. I know my Insignia RokuTV has no such setting to set the desired resolution, but I do not know if this is universal across all RokuTV manufacturers or the new Roku-branded RokuTVs.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102