I recently noticed a $4.99 transaction on my last bank statement. I was charged by Roku. I have roku devices and roku TVs. I subscribe to Netflix, Hulu etc. but I have never subscribed to the Roku channel.
Check you account for subscriptions: https://my.roku.com/account/subscriptions
If there's nothing there, are you sure it's really from Roku? There's a lot of scams out there using Roku's name.