Include the url of your app's page on Roku.com in newsletters, tweets, facebook posts, email newsletters, radio advertising, and create QR codes for the URL to use in Magazine and Newspaper ads, to put on refrigerator magnets, coffee cups, t-shirts, bumper stickers, hats etc. Traditional media isn't dead and might even be better than digital social media in some cases.
Word of mouth is still the way businesses succeed as far as I'm aware, so just get the word out and make it easy for people to find and install your channel.
- Joel