For OTA, all you need is a good antenna.
Roku is what I would call a menu provider.
You want to watch HBO or Showtime? Subscribe and add the HBO/Showtime widget to Roku.
You want to watch Disney? Subscribe to Disney and add the widget to Roku.
You want a package deal that gives you access to all the familiar cable channels?
--- There's ATTTVNow, YouTube TV, Sling, Hulu, etc, ETC. Subscribe to one or more and add the widget to Roku.
Amazon Prime? There's a Roku widget for that too...
The real confusion is how to get the best price for what you want to watch.... You can, for example, subscribe to HBO via Amazon or via ATTTVNow instead of subscribing to HBO directly.
Welcome to 2020.