I doubt he could topple the Romans,the supply line would be far too long for him to be able to do anything feasible.
But then,either way,this was later day Rome,in a hundred or so years they be ravaged by the Goths so Cao could probably break them.
"Two there should be; no more, no less.
One to embody the power, the other to crave it."
-Creed of the New Sith-