What is the Roman money called today?

There were 4 coins in ancient Rome.

A small bronze coin called an as was the least expensive.

A larger bronze coin called a sestertius was worth 4 asses

A silver coin called a denarius was worth 16 asses.

A gold coin called an aureus which was worth 25 asses.

In 301 AD the aureus was replaced by the soliduswhich, at the time, was worth 1,000 denarii.

In 312 AD the solidus' worth skyrocketed to 275,000 denarii.