Resolution:
The RESOURCE role is required during installation because when granting the RESOURCE role to a user, Oracle will also grant the UNLIMITED TABLESPACE privilege to the user. This is required because the installation queries the USER_TABLESPACES view using the check_dbtablespace_exists function to work out which tablespaces exists. If the user does not have the UNLIMITED TABLESPACE privilege, the installation will fail because the user could not see all the database's tablespaces and it will not be able to confirm that the TEMP tablespace exists.

You can remove the UNLIMITED TABLESPACE system privilege after the iPE install is completed and replace it with the appropriate tablespace level quotas. As for the RESOURCE role, you may also remove it after the iPE install is completed and replace it with the 8 individual system privileges.

SQL> select * from dba_sys_privs where grantee = 'RESOURCE';

GRANTEE                        PRIVILEGE                        
------------------------------ ------------------------------
RESOURCE                       CREATE TRIGGER                   
RESOURCE                       CREATE SEQUENCE                  
RESOURCE                       CREATE TYPE                      
RESOURCE                       CREATE PROCEDURE                 
RESOURCE                       CREATE CLUSTER                   
RESOURCE                       CREATE OPERATOR                  
RESOURCE                       CREATE INDEXTYPE                 
RESOURCE                       CREATE TABLE                     

8 rows selected.

grant create trigger to swpro;
grant create sequence to swpro;
etc.