ASP.NET Membership works on the aspect that your application will provide checks for the roles that a user currently belongs to and handle the processing of permissions from there.
Simply put, in your application code, you will have to insert something similar to handle verifying a user has permission to a function:
if (Roles.IsUserInRole("RoleName")) {
// Do something here
}
This essentially creates the premise of permissions, when a user is assigned a Role, they then can perform actions based on what the system allows them to in which the role(s) they belong to grants them the ability to do so.