Metepreter doesn't have root access on rooted phone

Question

I am currently testing how msfvenom for android works with it's source code. Well the AVD device that i'm testing is rooted but the backdoor doesn't have the root access. Runtime.getRuntime().exec("su"); didn't worked. Does anyone knows why it doesn't work?

Metepreter session's picture

 try
        {
            Process process = Runtime.getRuntime().exec("su");
            process.waitFor();
        }