register it as any user control:
<%@ Register src="~/BannerManagement/BannerRotator.ascx" tagname="BannerRotator" tagprefix="uc1" %>
<uc1:BannerRotator ID="BannerRotator1" runat="server" />
Only thing that you need to add to this are properties. Best would be to use Visual studio, intellisense will give you entire list and then copy it to your transformation.