The RadRotator is not working because it is not referenced in the clients-side script that is executed when the Left or the Right link is clicked. Since the rotator control is created on the server-side, the onclick handlers of the links should be registered on the server as well so that the RadRotator can be successfully referenced.
Also, I would suggest moving the links through which the RadRotator is scrolled in the user control that contains it as they are related in the custom scrolling implementation.
I have attached a modified version of the RadRotator user control to demonstrate the suggested solution. Please check it and change your actual project accordingly to resolve your problem.
the Telerik team
Consider using RadControls for ASP.NET AJAX (built on top of the ASP.NET AJAX framework) as a replacement for the Telerik ASP.NET Classic controls, See the product support lifecycle here.