It is free, but there's plenty of "premium" content that requires a subscription. Unfortunately, there's also plenty of scams out there. See the following page for more information about unrecognized charges:
Charges you don't recognize on your Roku account | Official Roku Support
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.
