I have three Roju Premier+ units in my home all on the same network. All three of them show up on the "Devices" tab of the Roku app for iOS.
In the Plex app for iOS I only see one of the three Roku's as a player.
Is there some setup I have to do on the other two players to allow them to show up as a player in Plex?
I don't recall every doing it for the one that works, but I may have just forgotten about it.
On a Roku you have to have already started the plex app before it will show up for other devices to control it. On some other devices (android TV for example) the controlling device can start it remotely.