i encountered this problem before on an ubuntu system, the reason was the application I was trying to launch needs the account to be a sudoer.
I type my root password, i type my account password it says wrong password.
I check the sudoer file, the account I was using was not included on the sudoers file, I edit the sudoer file and include the account I was using, it works fine.
You can duplicate the scenario, by let's say launching the backup tools in Ubuntu, it will ask for a password.
If the account used to launch the application is not included on the sudoer file, even if you enter the root password. It will prompt for a wrong password.
Once the account use to launch the backup tool program is included on the sudoer file, it will work fine.
But of course, different scenario different ways of approaching the problem and different ways to solve the issue.