session w/ user roles

Databases are not my thing... I mean I just don't get them. That being said, I have used codeigniter a while ago w/ grocery crud to try to learn this stuff and made something that worked but didn't touch it for a while and forgot everything. What I am trying to build is a log in with sessions where I can assign user rights based on roles. Do any of you know of any tutorials, pluggins, scripts or anything that would help me create this environment? I have found examples of sessions but roles are evading me.