You make the case that Stars is like HBO and Showtime, and yet HBO and Showtime both have Roku apps (albeit Showtime's is more of a teaser for the cable channel right now). Why couldn't Stars go the the same route as HBO (and Epix) and offer a Roku channel, but still tied to a cable subscription? I'm not suggesting that's the optimal outcome for end users looking to cut the cord, but that wasn't the question posed.
To me it's the same thing. Showtime doesn't have real content on the Roku, only commercials. HBO may as well not have because it demands you have cable, and an HBO subscription. Either way they are still telling me they don't want my money. Epix is even odder because most of their content is on Netflix. I really don't see a need for Epix having it's own channel.
Further Starz is in bed with Dish Network directly via the BB deal. If anything Starz will just pull further back and fold into the Dish family more completely. That might actually be the best bet for them short term anyway as premium cable is falling very fast right now.