You don't use webparts in transformations, you use controls. You'd have to look into the code of the Banner Rotator webpart to find out what control is being used and set the properties of that control as needed.
After looking at the webpart, these are the controls used:
<asp:HyperLink runat="server" id="lnkBanner" Visible="false">
<asp:Literal ID="ltrBanner" runat="server" Visible="false"></asp:Literal>
<asp:Image ID="imgBanner" runat="server" Visible="false" />
In the code behind it sets some properties but nothing I don't think you can't do in a transformation. Take a look at the code to get some ideas /CMSWebParts/BannerManagement