For those who didn't know -- which, until just a few minutes ago, included me -- there is a "Decades
" network that is carried over the air in 65 cities. It's a "classic tv" network similar to the much larger Me TV (around 200 affiliates) or Antenna TV (around 140 affiliates) in that it carries old TV shows from the 50s-80s. While there are 65 cities in the US where it's available over the air, it's available in more locations via cable systems.
To OP: A search of the Decades Website doesn't indicate they are available streaming in a standalone app on any device. There is no app in the iOS App Store, the Google Play Store, or the Amazon store.
Whether or not Decades ever has an app for any device is up to Decades. If they write one (or contract to write one) then they'll be on as many platforms as they decide they want to support. Currently, they're on 0. If your nearest affiliate is available via some "local channel" package on a streaming service like Sling TV, DirecTV Now, YouTube TV, or the like, you'll be able to watch via a subscription to one of those services. Check the individual services to see if they have a local channels package for your area, and if it includes your affiliate. I suspect they likely don't.So, when will it be available on Roku, or any streaming device? Possibly never. I wouldn't hold my breath.