Click on the login control and click the events lightning button. Double click on the LoggedIn event.

protected void Login1_LoggedIn(object sender, EventArgs e)

        {

            if (Roles.IsUserInRole(this.Login1.UserName, "administrator"))

            {

                this.Login1.DestinationPageUrl = "~/admin/default.aspx";

            }

            else if (Roles.IsUserInRole(this.Login1.UserName, "member"))

            {

                this.Login1.DestinationPageUrl = "~/member/default.aspx";

            }

            Response.Redirect(ResolveClientUrl(Login1.DestinationPageUrl));

        }