AV1 16x9 video displaying properly

Like I said, I don't know if/how "Display aspect ratio" is taken into account when the video is played back.  I can say that if there's black bars encoded into the video they will always be visible when played back on a Roku device.  When I rip a disc I always crop the black bars off using ffmpeg.

Unfortunately, the size and aspect ratio are not always tied together. Looking at one of my widescreen movies, I get

Width : 720 pixels
Height : 480 pixels
Display aspect ratio : 16:9

So as you can see, the width and height are the same as yours, but it is reporting a different aspect ratio. I have another DVD rip that I ran through Handbrake, because the image had black bands around all four sides. The difference in the video was that the latter was not mastered as an anamorphic image, so it had the black bars all the way around. I don't think MediaInfo identifies that setting, at least not that I can see after looking at several of my rips. My only solution for those incorrectly mastered videos was to either use Handbrake to alter the perceived video size (which doesn't always come out looking as good as you would hope) or find a correctly mastered disc, usually on Blu Ray instead of DVD. I've replaced several of my DVD rips with Blu Ray because the DVDs were not mastered as anamorphic, and the either had black bars around all four sides or the image didn't display correctly (usually either squished or stretched out). Fortunately I've never encountered a Blu Ray that wasn't done correctly. 

Is it a Roku specific issue? I don't think so, because as best I can recall the same movie looked the same with either a Roku or Shield as the player. And the Shield runs on Android, so I would expect it to not have the issue.