Ooh, a discussion on currency! What fun!

The primary currency of 1^st century Rome was generally based on silver - though you do have some gold and bronze coming in. From the least valuable to the most valuable!

• The As: Frequently, people will have some misconceptions concerning Roman currency regarding this coin. It wasn't often produced, and as the plural of the As is Asses, many people mistake it for, well...the donkey. Either way! It was the lowest denomination of the Roman coin, and by the late Republic, most currency was discussed in the forms of the...

• Sestertius. Crazily enough, with the modern conversion rate, the coin was worth roughly $1 USD today. It's the baseline for calculations on wealth in the Late Republic - For example, here's Plutarch discussing cheap housing that Sulla was forced to live in due to his relative poverty:

And afterwards, when he had at last become absolute in power, and was putting many to death, a freedman, who was thought to be concealing one of the proscribed, and was therefore to be thrown down the Tarpeian rock, cast it in his teeth that they had long lived together in one lodging house, himself renting the upper rooms at two thousand sesterces, and Sulla the lower rooms at three thousand. The difference in their fortunes, therefore, was only a thousand sesterces, which are equivalent to two hundred and fifty Attic drachmas. Such, then, is the account we find of Sulla's earlier fortune.

I'll talk about the Attic drachma in a sec, but I'll give you some more ideas on the sestertius. Some samples of the purchasing power of the sestertius:

• Basic pay for a legionary in the early 1^st c. was 450 sesterces per year. Julius Caesar doubled this to 900 sesterces - neither was a lot, but it was better than nothing. And then, of course, the officers earned just a tiny tad bit more, with the primus pilus (First spear - essentially the highest centurion of a legion) being paid 100,000 sesterces per year (Which is one reason that the "broke primus pilus" trope in HBO's Rome makes no sense whatsoever, but that's a bit off topic). As I said, just a tiny tad, eh? ;D
• The daily cash dole from patrons to clients was about 6.25 sesterces
• Price of grain per peck (According to Tacitus - might be within the first century AD, but it gives you an idea): 3 sesterces.
• Price of Martial's latest book (First century AD again): 20 sesterces.
• Admission to public baths: 0.0625 (1/16) sesterces
• Small farm (Pliny, first century AD): 100,000 sesterces
• From above - A room that a freed slave might have rented (think apartment): 2,000 sesterces per year.

Okee doke, hope that helped visualize the economy a bit! On to the next one!

• The denarius. This was the nomination that was most used (The sestertius was used for value, the denarius was used for...well...use. If that makes sense). The denarius was worth 4 sesterces and was made of silver (like the sestertius). These coins were often used as a form of advertisement by the politicians of Rome, sort of like pop up ads on websites - however, the first Roman to put his own face on a denarius was Julius Caesar, after he had been declared dictator for life. Often, the famous families would instead put things they were known for, as well as their names, on the coins - such as famous games, gods, or ancestors. For example, after he helped to assassinate Caesar, Brutus had coins minted with the name "Brutus" on them - and the face on those coins was his famed ancestor, who'd killed the last king of Rome. See the connection? ;)

• Finally, something that deserves a mention, because it's seen so damn much - the talent. A Roman talent was essentially just a method of measurement, more than a measure of value - for example, if tribute was required from a defeated nation (Let's use Carthage for example - they had an indemity to pay to Rome only a century earlier, and the talent didn't change any. The talent was 75 pounds worth of "x". In most cases, it's used to describe silver - And in Carthage's case, after losing the Second Punic War, they had to pay 200 talents a year for 50 years (10,000 talents - 750,000 pounds of silver - total).

Hope that helped out a bit! :) If you had more questions, let me know!