Channels are installed to your account, not a specific player. If you uninstalled then reinstalled on one, and the others don't check for updates during that time, they should be left alone. But if they update themselves while you have that channel uninstalled, they will be removed from the other devices as well. That's a good/bad thing with Roku players. Good in that once you've installed a channel on one device, it will appear on all the rest automatically. Just need to configure any logins necessary, as those are saved per device. Bad in that you remove it from one, it's removed from all. The only way around that is to have different Roku accounts for each player, but then you lose the good side of it.
Dan
Roku Stick (3600), Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.