This isn’t about the Roku specifically.
I am watching the movie “How It Ends” which is a Netflix original film. The vast majority of Netflix viewing in on 16:9 displays. These movies aren’t shown in theaters.
So why did Netflix film it in widescreen which puts a black bar above and below it? What benefit is it to Netflix?
.. or sometimes films going into the secondary markets in the US (sold to streaming services or direct-to-disk) are sold as theatrical releases in other countries.