The available roles are Administrator and Organizer. An administrator can do anything in the system: Contacts, Projects, Credentials, Configuration. An organizer only has access to the Projects area and they only have access to those projects they have been specifically assigned to by an administrator. They can not create projects on their own.
The ability to grant administrative rights is available to administrators in the system.
To do so, log into your system with administrative access and then click on "Contacts" and then click on the detail link for the contact in question.
Scroll down and on the right there will be a box labeled "Site Access". Click on the "Manager Site Access" button.
Then you can select the additional access level roles needed (default is volunteer, Organizer* and Administrator are also available) and then click on "Update Account".
*With the Organizer role, you will still need to assign the Organizer to specific projects for them to have access to that project.