To link Roku to hgtv and needs a provider.

Roku is not a provider... you would need a cable/satellite (like Spectrum, Comcast, DirectTV) or a streaming provider (like Hulu, AppleTV, among others) that include HGTV as part of the streaming package.  Some apps don't have free streaming, some apps have an independent subscription, and some require a provider that you have as part of a streaming/cable package.