Role management for Wordpress Multisite sites.

My not-for-profit site - causeinternational.com - uses WordPress Multisite and I want to allow regsitered users to create sites. Some of the sites will be "owned" by individuals but others will be owned by organisations - incorporated and not.

As straight WordPress has six predefined roles as described at http://codex.wordpress.org/Roles_and_Capabilities, is there any equivalent available with Multisite that the Super Admin user can also set up or over-ride on a site-by-site basis where necessary?