I subscribed to Britbox on Roku and I can view the app on the Roku channel, but the app itself won't add to my home screen. I pay for it through Roku
Subscribing to a premium service through The Roku Channel isn't the same as subscribing through the service's stand-alone app. I know it doesn't make any sense, but that's the way it is. If you subscribed through The Roku Channel, you'll have to watch through The Roku Channel. I don't think there's any way to put an icon on the Home Screen that links to it. I don't know why you can't add the stand-alone app to your Home Screen unless it has something to do with your Roku model or your location, but it wouldn't do you any good.