You might be able to use emby to populate the files on your phone, download them, convert them, however they get there. Then depending on file system access, which on Apple is so frightening. The roku app, which controls the remote control and such. Its just the normal roku app on the itunes store. I believe this has the ability play files over to the roku from within their app
Use this app, which is basically the roku remote contol to send these to your friends Roku from your iOS device on your friends local wifi network. This will work. At your friends just use this. You can do what you want today.
You can also use screen mirroring on the roku app to use MiraCast to do the same thing as you just wanted to do. This might work on Apple too. Roku calls it "pear"ing and shows a purple pear on screen and asks for permission for the device to broadcast to your Roku. Allow and presto. Pears btw, a clear jibe at Apple's airplay, and a nod to iCarly in one.
Two ways to choose. Be your own you, do it whichever way floats your boat.
The emby "play-to" casting (Roku ECP) only works if the Roku is on the same LAN as both your emby server and your Roku, so would've never worked for you in your use case anways.
But knowing you can still do it, as long as that Roku remote control app can see the videos emby downloads to your iPhone. If that is possible, we just solved the problem.
Edited by speechles, 30 September 2018 - 05:17 PM.