For the time being the RadRotor
control does not provide a client-side features that allow the next shown item to be set by its index. We already plan to add this feature in one of the next releases of the control and it is already in our ToDo list.
For now, you could use InitialItemindex - server property in order to achieve the same result. I recommend you use AJAX requests in order to avoid page flickering in this scenario. For your convenience I have prepared a sample that shows this approach and attached it to this thread.
I hope this helps.
the Telerik team