Roku operates via Internet connection and provides content through third parties like Netflix, Hulu plus, and Crackle. If you are looking to rely on Roku for current television you will need a Hulu plus account, and even that can’t guarantee all current television shows will be streaming.
According to the Roku site
they provide more than 150,000 movies and TV through subscriptions with Hulu Plus, Netflix, and M Go. Subscriptions to these providers are significantly cheaper than traditional monthly cable bills.
In addition to prime time television there are also several news, music, and family oriented channels. Sports channels and games are also available. The Roku purchase is a flat fee from $50 to $100 depending on the model you choose, all costs after that are Internet connection and subscriptions to content providers.