Hi Babu,
You can do this with any user which has been granted EXECUTE privileges on the _SYS_REPO procedures. Because this is a SYS_REPO procedure.
call _SYS_REPO.GRANT_ACTIVATED_ROLE(....)
Just check in your USER folder in Security, if your user id has that Stored Proc Execute access. If not, you need to ask the Admin to Grant you that access from Security Maintenance Screen. Else he can do this on your behalf, as in my case, I am doing.
I recommend, you can go through Thomas Jung Video to understand this concept better.
