@Serendipity12-
Although it has been frequently requested, normal Roku functionality does not include a quick return to the last viewed channel app.
To switch between channels viewed within the Spectrum TV app, this function Spectrum would have to have built this capability into the Roku-compatible version of their app. I can find no mention of this capability on the Spectrum website.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X