See the following from https://support.roku.com/article/360036652634
How to sign into the Apple TV channel
Before you can sign into the Apple TV channel, you must have an Apple ID. Use the instructions below to sign in with your existing Apple ID, or learn how to create a new Apple ID.
- Launch the Apple TV channel
- Select Settings
- Select Accounts
- Select Sign In
- Two sign-in options appear on your TV
- Choose Sign In On Mobile Device to sign in using your smartphone. You can either navigate to activate.apple.com and enter the code displayed on your TV, or scan the QR code that appears. Follow the on-screen instructions to complete the sign in process.
- Or, you can choose Sign In On This TV and enter your Apple ID directly on your TV screen using your Roku remote.
- If you do not have an Apple ID, select Create an Apple ID. You can either navigate to activate.apple.com and enter the code displayed on your TV, or scan the QR code that appears. Follow the on-screen instructions to complete the sign up process. You will be signed in automatically once you are finished.
For more information or help signing in, visit Apple Support.