I am not sure if I fully understand your question but if you are asking about Sitefinity'sability to read RSS feed from another site and show its contents, the answer would be no as Sitefinity does not have an RSS reader currently. For the time being it only writes information from the database into a stream in RSS format and affords RSS readers applications to read from it.
If you want to achieve such fuctionality it would be a bit easier to use the RadRotator indeed. You will only need to copy the code from the live example here: http://www.telerik.com/DEMOS/ASPNET/Rotator/Examples/Functionality/LiveXML/DefaultCS.aspx
and to wrap it in a user control. It would look something like this:
<%@ Control Language="C#" ClassName="InTrayBoxHeaderTemplate" %>
<%@ Register TagPrefix="radr" Namespace="Telerik.WebControls" Assembly="RadRotator.Net2" %>
<radR:RadRotator id="RadRotator1" runat="server" DataMember="item" ContentFile="YourContentFile.rss"
TransitionType="scroll" width="500" height="400">
<div class="module" style="height:360px;overlfow-y:auto;">
<a href="<%# DataBinder.Eval(Container.DataItem,"link") %>" target="_blank"><%# DataBinder.Eval(Container.DataItem,"title") %></a></strong>
<%# DataBinder.Eval(Container.DataItem,"pubDate") %>
<%# DataBinder.Eval(Container.DataItem,"description") %>
In this code you will need only to change the ContentFile
property to point to the preferred location. Add the control into Sitefinity and it should work just fine.
Please, let me know if I am missing something.