From about 100 BC onwards, Legionaries received the sum of 225 denarii a year for their service. (The denarius
was a silver coin with a weight of approx. 4.5 grams. Its initial value was put at 10 asses, yep asses, giving the denarius its name which translates to "containing ten".) This basic rate remained unchanged for many years until Domitian increased it to 300 denarii. There was no further rise until the time of Septimius Severus, who increased it to 500 denarii a year. This base salary wasn’t an emperors ransom, but wasn’t bad either considering the perk- each soldier would have his pay supplemented by the booty taken in a campaign.