For there to be a working audio description of what is taking place on the screen, the creators of the programming must have included an alternate audio file you can select which contains the narration. Not all programs have such an alternate audio file, in fact I'd say most do not.
If you are watching such a program and have selected the appropriate audio file, THEN your Audio Narration volume setting should apply.
The Roku default method of accessing your choice of audio track is to press the * key on your Roku remote while viewing the program and examining the options presented. The options presented will vary depending on the options available for any particular program.
But more and more channels are not using the Roku default but substituting their own method of access -- I'm guessing this is so they will have consistent controls with versions of their app running on platforms other than Roku. Often these options are accessed by pressing the up and/or down cursor control keys while viewing the program to pop the channel's own control options on the screen.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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