Lastly, you should follow the recommendation, available e.g. in SQL Reference book:
CONNECT, RESOURCE, and DBA roles:
These roles are provided for compatibility with previous versions of Oracle Database. You can determine the privileges encompassed by these roles by querying the DBA_SYS_PRIVS data dictionary view.
Oracle recommends that you design your own roles for database security rather than relying on these roles. These roles may not be created automatically by future versions of Oracle Database.