Why am I getting charged $10.99 for Roku channel

Roku doesn't charge for a Roku account but you can subscribe to other services (e.g., Netflix) through Roku.

If the charge is directly from Roku (All transactions from Roku will appear on your billing statement as “Roku,” “Roku for <app/provider>,” or "The Roku Channel."), see information in https://support.roku.com/article/218368088

If the charge is billed through Apple:

This is primarily a user-to-user support forum; other Apple users like you. We don't have access to information about charges to your account. Apple has a support article about charges — see each of the steps in the following instructions. They include information on contacting Apple Support if the other steps don't help. See: If you see 'apple.com/bill' on your billing statement - Apple Support