I've had two Roku TVs, and I've never seen a resolution setting on them. The Roku players, yes. But not TVs. You can't change the resolution on the TV, that's fixed. Or are you referring to some other display settings?
Nvidia Shield, Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.