). In your installation folder a folder Scripts
should exists. It contains the scripts that every control needs in order to operate properly. You can also check this help article
for additional information.
Onto your particular question:
On a blank new page I added the controls that you mentioned: RadScriptManager, RadStylesheetManager, RadAjaxManager, RadWindow and RadRotator.
I removed all RadControls from the page and added just the MS ScriptManager (ScriptMode = Release) and the result was 67KB.
the Telerik team