Over-the-top online video and TV device maker Roku is adding more digital channels to its gadgets whilst building out an advertising business to augment its original paid video background.

“We’re launching over 90 channels a month,” business development VP Scott Rosenberg tells Beet.TV. Roku added Yahoo Screen, WatchESPN and Sky Store over the last few months.

“We had our start around subscription and transactional services like Netflix and Amazon Prime,” Rosenberg adds. But the ad-supported segment is one of our fastest growing … in terms of the number of apps coming to the platform and usage.”

Roku is working alongside some ad-supported channel operators to develop ad formats that work wlel on its platform, including Sony’s Crackle, which is running interactive 30-second spots via Roku.

Rosenberg spoke with Beet.TV at Brightcove’s PLAY customer event in New York.