Hi, If you are using aspnet membership you can try:
if (Roles.IsUserInRole(txtUsername.Text, "Role1"))
Response.Redirect("~/System/Role1/Default.aspx");
else if (Roles.IsUserInRole(txtUsername.Text, "Role2"))
Response.Redirect("~/System/Role2/Default.aspx");
else if (Roles.IsUserInRole(txtUsername.Text, "Role3"))
Response.Redirect("~/System/Role3/Default.aspx");
else
Response.Redirect("~/Default.aspx");