Yes, RadControls Prometheus does not provide a way to load their scripts from external files, e.g. EnableEmbeddedScripts is always true (and actually this property is not present in Prometheus). Regarding the speed optimization, you could try the RadScriptManager (currently hidden in Telerik.Web.UI) which will combine and compress all scripts from the Telerik.Web.UI assembly. This control is currently the same as AjaxControlToolkit's ToolkitScriptManager, but will be updated in one of the next hotfixes to avoid some of the limitations of its toolkit counterpart.<telerik:radscriptmanager runat="server" id="RadScriptManager1"></telerik:radscriptmanager>
<telerik:radeditor runat="server" id="RadEditor1"></telerik:radeditor>
If your scripts are WebResources, you could add the following assembly attribute in your application, which will force RadScriptManager to combine and compress both Telerik.Web.UI's scripts and your scripts.[assembly: Telerik.Web.UI.ScriptCombine]
Note that this control is currently in development and you could have problems using it. Please, let me know how it goes.
Valeri Hristov (Senior Developer, MCSD)
the Telerik team