Who'd win in a battle between the Roman Legions during the time of Augustus and the Mongols during the time of Ghenghis Khan?

Sorry, but your submission has been removed because we don't allow hypothetical questions. If possible, please feel free to rephrase the question so that it does not call for such speculation, and resubmit Otherwise, this sort of thing is better suited for /r/HistoryWhatIf.