This sounds like a film for English release with the captiononing built right into the screen image.
Black boxes with English text ("street noise", etc.) sounds like optional traditional English closed captioning selected on the Roku. This is electronically superimposed over the image by the Roku at the time of viewing. If the closed captioning source data for that program doesn't specify where to place the caption on the screen it typically is centered at the bottom of the screen. If that's where the captioning on the film is placed, it may get obscured.
Make sure the closed captioning option on the Roku is turned off for this film. 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.
But more and more channels are not using the Roku default but instead 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.