Role Management

I am developing a website in Visual Studio 2005 using ASP.NET 2.0 technology. Using the Web Site Administration Tool, I have changed the website to use Forms Authentication, created a few users, turned on Roles, and created a couple of roles which I then assigned to the users.

Now on my web form I placed the ASP.NET Login control on the form. It works perfectly and I can login and logout and everything. My problem is that once the user has logged in, I want to check which role he is in so that I know where to redirect him. I use the following code in the Login1_Authenticate event (Login1 is the name of the Login control):

Select Case True
    Case User.IsInRole("Teacher")
        Response.Redirect("~/Teacher.aspx")
               
    Case User.IsInRole("Parent")
        Response.Redirect("~/Parent.aspx")

    Case User.IsInRole("Student")
        Response.Redirect("~/Student.aspx")
End Select

But it goes right through the Select Case block without any of the cases being true. Now those are the only roles I have defined, and every user belongs to one of those roles, so one of them should be true! I tried moving the code to the Login1_LoggedIn event rather, but same problem. I even tried it on the Page_Load event and nothing. If I check the User.Identity.IsAuthenticated method, it returns false. But the user is definitely logged in because if I type the wrong username or pasword it complains, and as soon as I type the correct username and password then it's fine. Any ideas? Thanks