I am trying to completely remove any credit card attached to my roku that I just set up due to it being stolen (at work).
Help!
Your CC information isn't stored in the Roku itself, it's in your user account. You can delete it from the user web site. The Roku might display a few of the digits, but no one is going to be able to access your complete CC information from the Roku.
Also on your user web site you can delete the device from your account, so it cannot access your account at all if they put the device back online.
@Fawkwad -
Your CC number cannot be revealed on the Roku interface, so until you remove the stolen unit from your Roku account as @atc98092 suggests, all the thief can do is make normal Roku transactions through your Roku account. Things like add a premium streaming service that can only be accessed through your Roku account, add a pay per view session or screen saver to your account, purchase Roku equipment, etc. The thief won't have general access to your CC to use anywhere else.
Log into your account at https://my.roku.com, scroll down to the "My devices" section, click on the stolen device, and remove it from your account.