The user will "by default" not be associated with any roles. There is a table in the datavase called aspnet_usersinroles which handles that. It has an entry for each role a user has. When you develop role management pages their job is just to manage the rows in that database table.
This is a very in depth series on membership if you want to learn about membership.
http://aspnet.4guysfromrolla.com/articles/120705-1.aspx
I hope that helps,
Brendan
C. Brendan Enrick
Brendan's ASP.NET Advice BlogMake sure you click "Mark as Answer" for any post which has helped you. This will give recognition to those helping others as well as earn you a point. It also helps people know which posts still need work.