Is there any built-in way to map Oracle database roles to Microsoft Active Directory groups?
You want to manage your users, roles and user to role mappings in AD?
I think Enterprise User Security is what you want, see http://docs.oracle.com/cd/E11882_01/network.112/e10744/concepts.htm#autoId10
Basically you'll need Oracle Enterprise Edition, and, after you've configured your database to use your directory (see http://docs.oracle.com/cd/E11882_01/network.112/e10744/getstrtd.htm#CBHDBFGC ), you can create your users and roles as CREATE USER x IDENTIFIED GLOBALLY; CREATE ROLE y IDENTIFIED GLOBALLY;
You can assign privileges to role y, but you should manage user to role mappings in AD.