Two different types of boxes. If your thinking of a SlingTV subscription, you need a Roku or another streaming "App" box. If you want to remotely watch TV from a Cable/SAT set top box you need a Slingbox. You can download the Sling Player app on a Roku, but thats only if you have a Slingbox to stream another Cable/SAT box from.
I'd recommend doing some research, not the same type of boxes.