Sorry I'm still not clear on this. My elements are nested, so it's not that I have more than one root element, I have to iterate within an iteration e.g.
<CATALOGUE>
<PRODUCT>A<SKU>1</SKU><SKU>2</SKU></PRODUCT>
<PRODUCT>A<SKU>1</SKU><SKU>2</SKU></PRODUCT>
</CATALOGUE>
So in the above example, one input drives <PRODUCT> and another iteration within that is required to produce the <SKU> elements. However, because they share the same root, and each input can only have one loop element, it doesn't seem possible.
The closest I've got to that is using tFileOutputMSXML, but it doesn't reliably put the elements within the same structure as it seems designed for multiple root elements, not nested loops.