The legality is not the issue. It is extremely unlikely he will be prosecuted for lying in a civil case. The issue here is that the statements make him look bad and endanger his own case. You seem to think that person will lie when lying makes it likely he will lose a legal case and lose millions of dollars, where telling the truth would help his case and protect the money. Explain why you think anyone would do that.
People usually lie to get something for themselves, not to deliberately lose a fortune. Explain why you disagree. Give us some examples of people who lied in order to destroy themselves.
OMFG! People lie for many reasons, good or bad ones, stupid ones. Logical ones even totally incomprehensible ones. I know that. That has nothing to do with it. The simple and only important question here is if You are Accusing Rossi of lying under oath?