Here is a simple way to do the role based Authorization in your MVC4 Controllers using VB.NET
IF you have a role called Client then simply add the following text on top of your each ActionResult( which displays the view)
See the following example. The Index View has been restricted and can only be viewed by someone in the Client role.
<Authorize(Roles:="Client")> Function Index() As ActionResult Return View(db.Purchasers.ToList()) End Function