got an email for an upgrade charge I didn't authorize. It's not a subscription. Wtf is going on!!!
Sounds like a scammer trolling. Who was it from? How do they want you to respond? What phone number or website do they want you to go to?
And finally, did you ever pay somebody for Roku support and/or device registration in the past? Roku does not charge for these, so this could be how some scammer got your email address.