User/Role management using existing Database (Web form)

Question

I am want to make a web site which admin account can add roles. i want each role to be able to create users with certain roles . for example ADMIN can add any role! but a SUPPERUSER can create users with FOO role only and ... ! because of this purpose i don't want to use the default ASP.Net database for user/role managment.

I used aspnet_regsql.exe to add user/role management to my existing database. here is the web.config file ! the problem is i don't how to add user/role in my existing database! web config file :

<membership defaultProvider="CustomizedProvider">
  <providers>
    <add name="CustomizedProvider"
 type="System.Web.Security.SqlMembershipProvider"
 connectionStringName="Emtehani"
  />       
  </providers>
</membership>
<profile>
  <providers>

  </providers>
</profile>
<roleManager enabled="true" defaultProvider="CustomizedRoleProvider">

  <providers>
    <add name="CustomizedRoleProvider"
         type="System.Web.Security.SqlRoleProvider"
         applicationName="/"
         connectionStringName="Emtehani" />
  </providers>
</roleManager>

NOTE

I am using Web From project so i can't use Web site administration tool to add user and role ! . i want to add users using C# codes ! please give me an example of how to add user/role to my existing database !