Hello Pamela,
We offer a Roku network app tied to our network platform. Blubrry.com/explore/ is a good example how our network platform works, we pull RSS feeds from other sources then re-package the feeds into an API service to feed Roku apps. The API works with other platforms as well, such as Samsung Smart TV apps, Android TV and others. Please contact us for a quote on custom network website and Roku app.
There are other sources for Roku apps, the solutions I have seen though are not network based they are individual show based. Individual show apps are more cost effective as you can simply feed the app with the RSS feed directly. Networks are a bit more complicated plus providing search mechanism for multiple feeds from a central place is just one of the many challenges you would have to figure out if going on your own.