Mr Rouhani and Italian Prime Minister Matteo Renzi spoke at Rome's Capitoline Museum after Italian firms signed business deals with Iran.
But several nudes there were hidden to avoid offending the Iranian president.
Italy also chose not to serve wine at official meals, a gesture France, where Mr Rouhani travels next, has refused to copy.
An Islamic republic, Iran has strict laws governing the consumption of alcohol.
Mr Rouhani is in Europe on a five-day tour seeking to boost economic ties after the implementation of a deal on rolling back Iran's nuclear activity saw sanctions lifted.
"Iran is the safest and most stable country of the entire region," the Iranian president told Italian business leaders.
He also stressed growth would be key to combating extremism, saying "unemployment creates soldiers for terrorists".
Monday saw contracts worth around €17bn ($18.4bn; £12bn) signed between Iran and Italian companies.
On Tuesday, Mr Rouhani also met Pope Francis, who urged Iran to work with other Middle Eastern countries against terrorism and arms trafficking, the Vatican said.
Iran has been accused of funding militant groups, such as Hezbollah in Lebanon.
Mr Rouhani asked the pontiff to pray for him, and gave him the gift of a hand-made carpet.
He travels to Paris on Wednesday where more deals are expected to be announced. An agreement with Airbus for the purchase of more than 100 aircraft is due to be finalised.
Italian hospitality for the visiting Iranian President Hassan Rouhani has stretched to covering up nude statues.