When an issue lies with the provider of a specific channel.

I usually follow the privacy page link from the Roku channel store, then browse around their website until I find the “contact us” page.  I agree that it could be easier though.  I suspect that when originally designed, they expected every channel/app to be someone large and well known like Netflix, but I think they should add a direct contact page link since some of the apps are from fairly obscure companies.