How to find user role with IdentityHelper, then redirect

How do I find the role the user belongs to then redirect to a page in the Admin folder if they belong to the Admin role.

    Protected Sub LogIn(sender As Object, e As EventArgs)
        If IsValid Then
            ' Validate the user password
            Dim manager = New UserManager()
            Dim user As ApplicationUser = manager.Find(UserName.Text, Password.Text)
            If user IsNot Nothing Then
                IdentityHelper.SignIn(manager, user, RememberMe.Checked)
                IdentityHelper.RedirectToReturnUrl(Request.QueryString("ReturnUrl"), Response)
            End If
        Else
            FailureText.Text = "Invalid username or password."
            ErrorMessage.Visible = True
        End If
        End If
    End Sub

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