When setting ItemWidth, ItemHeight, Width and Height properties, please note that in case you have the buttons enabled for the rotator, you need to reserve 40px for them as well (the buttons are 20 pixels wide). So, if you have an ItemWidth of 200 pixels for example, your Width property should be set to 240 pixels.
I hope this helps. If you still experience problems, please open a support ticket and send us a sample project that we could check locally.
the Telerik team