The previous owner would have the charge on his account and his card, so I don't think you would see that charge on your credit card, unless you are using the same login and same credit card as the previous user.
If you didn't authorize that charge or subscribe to anything, you should dispute it with your bank/credit card.
If you have a subscription you signed up for through Roku, then that may show up as a charge with Roku and not necessarily describe it correctly. Check to see if any of your subscriptions match that charge.
