Maybe still confused.

You can get HBO GO on the Roku, but not with your TV provider.
First, separate HBO GO from everything else on Roku. Now separate who your internet provider is.
No matter who your internet provider is, while there may be limits to how much data you can stream in a month, they are not blocking programming to the Roku, that includes Roadrunner, or Charter, Fios, ATT, or whoever.
Now to get HBO GO you have to subscribe to HBO. Whoever you have for a TV provider that you get HBO from then has to have an agreement with HBO to allow you to watch HBO GO on the Roku. Most all allow you to get HBO GO on your computer or mobile device, but some do not have an agreement to allow you to sign up on the Roku for it. You have to verify you subscribe to a provider that has that agreement before you get HBO GO on the Roku. So for instance Dish Network allows you to watch on a Roku. Direct TV does not.........
Other programming for the most part is not the same on a Roku. Some is very similar. For instance to watch Amazon movies you have to have an Amazon account. But to watch Al Jeezera, or Euronews, or hundreds of other programs, you just add it and watch it.