If you have already navigated to your Roku Account dashboard and confirmed there are no subscriptions, then it as you suspected, most likely a fraudulent charge. There is no charge for the Roku Channel or Roku platform as a whole. There are no activation, setup, or maintenance fees. Also, look under Purchase History. These are the two locations for Roku charges.
https://my.roku.com/account - login to check subscriptions and Purchase History.
https://support.roku.com/contactus/ - Billing. Another way to confirm with Roku.
Would definitely let your credit card know this an unapproved/fraudulent charge upon confirmation. They have the details regarding point of sale and can end this recurring charge.
