I use the Roku boxes as a replacement for cable boxes and use the cable TV app (in my case Spectrum) to view the channels I have as part of my cable package. If you have a Roku that uses voice commands, your mom could simple say "Hey Roku, Open Spectrum TV" or something similar if it is Comcast, DirectTV, or one of the others, assuming they have a streaming package app. Then it is a matter of showing her how to navigate through the cable guide and select a channel.
Another alternative is Xumo, which I haven't used, but I understand it has a number pad on the remote for channel changing, which currently the Roku doesn't have, but would work similarly in regard to cable.
