Showtime Networks has launched its authenticated streaming-video service on Roku broadband set-top boxes, providing access to to hundreds of hours of on-demand content and live TV feeds, available to subscribers of several major pay-TV partners.

It’s the first time Showtime’s Internet-video service is available on a TV-connected device. But customers of Comcast are out of luck: The nation’s largest cable operator is not allowing its Showtime subs to watch the premium cabler’s content through Roku devices. Similarly, Comcast blocks customers from accessing HBO Go on Roku boxes.

Asked about Comcast’s policy of excluding cable network apps for Roku, a rep for the cable operator claimed the issue is related to developing support for individual devices. “With every new website, device or player we authenticate, we need to work through technical integration and customer service, which takes time and resources,” Comcast spokesman Steven Restivo said. “Moving forward, we will continue to prioritize as we partner with various players.”

Currently, the Showtime Anytime service on Roku is available through DirecTV, Time Warner Cable, AT&T U-verse, Verizon FiOS and Cablevision Systems’ Optimum TV. The CBS-owned cabler’s “TV Everywhere” service is available at no additional cost to Showtime subscribers of those pay-TV providers.

Programming available through Showtime Anytime includes current and past seasons original series including “Homeland,” “Ray Donovan,” “Masters of Sex,” “Californication,” “House of Lies,” “Dexter,” “Web Therapy,” “Episodes” and “Nurse Jackie.” In addition, customers have access to Showtime’s live East and West Coast linear feeds, as well as comedy specials, documentaries and sports programming on their Roku player.

The Showtime Anytime app on Roku features include a “my list” feature for subs to organize and view their favorite programs; play shifting, to resume watching a program paused on another device; and the ability to share viewing selections on Facebook and Twitter.

Showtime Anytime also is available on the web, on Apple iOS and Android devices, and Amazon’s Kindle tablet.