Just had a quick play around with Subtitles on both the Netflix App and Amazon Prime Video App and from my brief testing on the Roku Stick +, i couldn't remove the black background box with the subtitles text on it when watching Netflix or Amazon Prime Video (unless somebody knows how who uses subtitles on these two services?).
Only the NowTV App for me where i could remove the background box that contained the subtitles text in the Caption customised settings.
Both Netflix and Amazon Prime apps have their own subtitles appearance settings, at least on my Samsung TV. Of course it might be different on the Roku stick.
It's definitely good news they work as expected on the Now TV app though.
Just swapped back to my NowTV 4K box and tried the Netflix App on the box and with the NowTV box Netflix App it is not showing the black background box on two titles i tried which was Oblivion and The Martian (which is good news).
When i tested the Netflix App on my Roku Stick + i only checked out the movie Deadpool , so i just checked Deadpool on my NowTV box Netflix App and this also has the black box showing behind the subtitles text (so the Netflix App must be content related if it has the black background box or not).
Won't have time to check my Roku Stick + again because it's plugged into my Home Cinema Amp in another room and it's a pain to plug in and out.
I might be getting the wrong end of the stick here and feel free to tell me if I am.
if you're having issues with the appearance of subtitles on Netflix. Then be aware that subtitle appearance is determined by settings on your Netflix profile. These settings can be changed by going to the Netflix website subtitle settings on the box/stick should have no bearing on the appearance of subtitles in Netflix
go to the following URL
then expand the profile and parental controls for the profile in question and click subtitle appearance.
From here you should be able to change how subtitles appear within the Netflix app. Be aware that you will have to completely restart the Netflix app in order for the settings change to take effect in the app on Roku/now TV device. The easiest way to do this would probably be to restart the device
Hope this helps and apologies if I have the wrong end of the stick😀