The Romans could take this , but they would have to barrage the oncoming zombie horde with firey 'shells' from their catapults. Fire always works well on Zombies ...
Otherwise their screwed , because as Khan mentioned the Gladius is a stabbing weapon (Technically it could be considered a long knife) while their armour (aside from the body length shields) isn't particularly good.
Although I'd love to see a group of Romans try the 'tortoise' maneuver on the zombies , but it would be more of a suicide attack then anything.
....wait a minute is this real romans or modern day recreations who dress up as romans ๐ Because Modern day romans would have the advantage of the pope. Holy 'power' like that usually causes zombies to drop like flies.