Purpose
Use this statement to delete a role.
Prerequisite
You need to have either the system privilege DROP ANY ROLE or a role with the WITH ADMIN OPTION is assigned to the user. 
Syntax
drop_role::=
                                                                         
                                                                    
Usage Notes
- If CASCADEoption is specified, all of the schemas of the role as well as their contents will be deleted.
- If schemas that belong to the role still exist, CASCADEmust be specified or these must be explicitly deleted beforehand by usingDROP SCHEMA.
- This statement will also remove the role from other users who are associated to it. However, open transactions of such users are not affected.
- If the optional IF EXISTSclause is specified, then the statement does not throw an exception if the role does not exist.
- If you have created a role, it does not meant that you can delete it.
Example
DROP ROLE test_role;