It looks like Roku, being a closed system, has disabled sideloading.
Most sites I looked at recommended Amazon fire sticks and such... honestly, the Apple TV and Plex is my go to mix.
That being said, most of the sites that mentioned Roku, said that Plex was the better route to go.
It might be a good time to look at Plex *My Fav* and set up your own plex media server with a spare PC. Load your media on the plex server, and then watch from the roku, or any other device you can install the Plex app on. The Plex app and the server are both free.
If you use a seedbox, many seedbox providers well sell you a Plex package... so storage and speed are taken care of... my seedbox with Plex from Evo Seedboxes * as a backup* is roughly 25 dollars a month. If you don't have a ton of money or an old computer laying around, 25 bucks is cheaper than some alternatives, and chances are, if you use this site, you have a seedbox, so why not use it for more than one thing?
If you have a google drive, with unlimited storage, you can place your media in the cloud, and after installing google drive on your Plex media server, you can map those over to your Plex library. As long as you have a decent internet connection, you should be fine with this, but, local media on an SSD drive is always going to be available, even when the internet is out. I trust Google to honor my 12 dollars a month pricing, for a while... but not forever.
Like everything else, if you really want to keep something, DON'T store it on a Cloud... store it on a local media, or three. Hard drives die. DVD's and Blu-Ray's get scratched. Backups get corrupted... by using all three methods, you narrow your window of disaster down tremendously.
