How do I behave my application's logged in same as asp.net logged in

Hello everyone! By reading my question, you would get the idea. I'm working on application that requires user login information to access to members-only resources/pages and these pages/resources are specified to user roles. My question is, when I verified from database that user is valid user, how can I register him in a way that satisfy in web.config file. like: <allow roles="MANAGER" />
<deny users="*"/>
How to implement this functionality? How does asp.net application verifies that current user is admin or just user?. My efforts:
I tried to override role provider class, I just only need following function (which calls automatically itself when user visits that specific directory which is admin only) 

Public Overrides Function IsUserInRole(username As String, roleName As String) As Boolean If String.IsNullOrEmpty(username) Or String.IsNu ...