I cut the cable a few years back, got roku and an indoor antenna and then an outdoor antenna and I can receive lots of channels OTA many in high definition.
roku has any free channels available but you need an account to add them.
as far as antenna tv try this site to see what ota signals might be available in your area.
Are you aware you can add these channels from your TV screen?
No need to remember your account when visiting Add from your HOME ROKU page
To order on the net:
https://blog.roku.com/
https://blog.roku.com/category/us-roku-channels