Assuming that you can still navigate your Roku's menus, you can factory reset it.
Navigate to the Settings menu.
Choose Advanced System Settings.
Click Factory Reset.
Enter the code on-screen.
Locate the Reset button on your Roku.
Hold down the reset button until the device actually resets.
Resetting your password. Go to my.roku.com/password/reset on your computer or smartphone. Enter your email and select Submit. Roku will send a password reset email if an account exists for that address. https://www.wikicue.com/roku-password-reset/