They had large war machine like catapults called ballista that fired arrows and a sort of giant catapult that fired massive pieces of rock.
The bolt would probably have been fired by artillery such as a ballista, which was a type of large crossbow.
The Romans adopted these weapons during the Punic Wars and further developed them, before introducing the new arrow-firing ballista and stone-throwing onager.
The Medieval Catapults used during the Middle Ages were the Mangonel, the ballista and the mighty trebuchet.
A great feature is that new combos and actions are displayed during the action of the game at the appropriate time (such as how to use a ballista).