Well, lead did infect the denarius and debase it to such an extent that it was almost as worthless as the Federal Reserve Note vs the U.S. Dollar.
The Roman Empire had a better grasp on what currency is than a lot of people today. Currency can’t be debased, because the government defines what it is. The supply of gold has always been too small to support a huge economy, which is what Rome had. At its peak, the Empire had a substantial fraction of the entire world’s population, and the Roman economy was enormous, having a major impact on the economy of India, and trade as far afield (uncontroversially) as China and (controversially) the Americas.