To enable combining web resources with Telerik extensions, you need to register WebAssetHttpHandler in your webconfig:
IIS 7
<add name="AssetHandler" preCondition="integratedMode" verb="GET,HEAD" path="asset.axd" type="Telerik.Web.Mvc.WebAssetHttpHandler, Telerik.Web.Mvc"/>
IIS 6
<add verb="GET,HEAD" path="asset.axd" validate="false" type="Telerik.Web.Mvc.WebAssetHttpHandler, Telerik.Web.Mvc"/>
, Script StyleSheet. - Telerik:
http://www.telerik.com/help/aspnet-mvc/web-assets-working-with-javascript-web-assets.html