HOW DO I SET MY ROKU TV TO THE DISH CHANNEL
I can find no DISH Channel for Roku. If you have a DISH receiver connected to your tv, just set your tv to display the HDMI input to which DISH is attached.
Also, you can install Roku channel apps for a number of channels carried by DISH that you can then access using your DISH account login credentials. Per this DiSH page (https://www.dish.com/availability/ways-to-watch/streaming-sticks#roku) these are:
ESPN, SHOWTIME, STARZ, CNN, FOX NOW, ABC, A&E, Freeform, Disney, NBA, History Channel, Lifetime, National Geographic, Cooking Channel, DIY Network, Epix