Factual error: The weaponry of the Romans and their use is wrong (as they are in all Hollywood movies playing in the Ancient Mediterranean that I know): Instead of one spear, each legionary would carry two weighted javelins, called Pila (singular: Pilum), which had a long narrow iron head. The purpose of these were to throw them at the enemy before melee; if they did not kill their targets, the pila would get stuck in their shields. The head shaft would bend, making the pila useless for 'return' to their original owners, and with the added weight of the javelin, the enemies' shields were rendered useless as well. Following this, the Romans attacked with short swords (the Gladii; singular Gladius).
Factual error: The armor and shields of the legionaries are of a type not used until over 100 years later, and there are no transverse crests identifying centurions.
Factual error: Several things are wrong in the gladiatorial fight between Spartacus and Draba. Spartacus fights as a Thracian (thraex), but his sword is wrong (it should be the curved sica), his shield is much too small and his helmet and shin protectors are missing. Draba fights as a retiarius, but that type of gladiator was only introduced under emperor Augustus, some 60 years after the slave revolt.