Check if the Phone is Rooted
Look for Root-Related Applications
When a phone is rooted, the process often involves installing an application to manage root access, most of the time SuperSU. One first step is to check if the SuperSU application is installed. You can check directly for the icon in your main menu, or go to Settings > Applications and search the application.
Check with Root Verifier
Once installed, you can launch the application. The interface is really simple, you just need to click on "CHECK" and wait for the result.