There are a few options.

You can change the names of the exiting roles through "Edit Group Properties". All the non-student roles have the same permissions so you can just rename them.

If you need new permissions for your role then you need to explain more about what you are trying to do.

Dinesh the user type is local to dotlrn and dotlrn is a vertical application built on the modules of openacs. You must try to use the approach followed in the dotlrn create scripts in your application. But I would suggest you could use a simpler approach for your application by directly using the groups api for handling roles.