C-SPAN availability

C-SPAN has never been available on OTA stations. It was created in 1979 by the cable companies. It is now considered a cable and satellite provider. There is one radio station in Washington DC that broadcasts the audio, but there is no other OTA availability. 

Roku cannot "license" their content. C-SPAN themselves would need to develop and offer an app for Roku devices. Based on the information I can find, the only online source for C-SPAN content is on their own website, and it's only available to cable/satellite subscribers. The only apps that appear to be available are on iOS and Android platforms, and again you must be a cable/satellite TV subscriber to access the content. It does appear to be available via streaming TV services, such as YouTube TV, Philo, Sling TV, Fubu and Hulu, which all offer cable TV subscription services.