.The contact between the Romans and the people of Sanatana Dharma is quite ancient.
People from the region from where the Romans ruled later, were transacting business with India right from Sanatana Dharma Vedic times.
The civilizations which preceded the Romans, Minoans, Sumerians had contacts with the Vedic people.
By Till Niermann – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=388210
Vedic texts refer to there areas as Yavana, though it is normally taken s denoting the Greeks.
Yavanas are referred to in The Vedas,Mahabharata and Tami Literature speaks in detail about Yavanas.
The Great Tmail epic Silappdikarm, which is set in the background of Madurai and Poompuhar, called as Kaverippompattinam mentions that Yavanas hd a flourishing Trade with all the Tamil Kings, Chera, Chola and Pandyas.
The items exported to Rome /the area under which Romans ruled were,
Tigers of Four varieties,
Pliny states that Nero paid one million sesterces for one cup of Emerakds from India!
Iron and Steel.
Imported in India from Rome.
Ornamental pieces like vases,
The trade reached its peak during the period of Augustus and the Roman currency depreciated alarmingly.
During Augustus’s period ratio of Gold to 1:9.3 aureus, aureus being 25 Silver Dinari.
Because of the heavy import from India, the ratio became 1:96 during the period of Nero and this economic decline was one of the reasons for Rome’s .disintegration as an Empire.
‘The recorded history of the city goes back to the 3rd century BCE, being mentioned by Megasthenes, the Greek ambassador to India, and Kautilya, a minister of the Mauryan emperor Chandragupta Maurya. Signs of human settlements and Roman trade links dating back to 300BC are evident from excavations by Archeological Survey of India in Manalur’
Romans, because of the high volume of Trade settled in India in great numbers.
They had a colony for them Roman Colony. In Madurai.
As is the wont they even built a Temple for Augustus in Musiri.
Periplus mentions this.
Towns mentioned by Grrek Roman Historians.
Point Calimere( kodiyakkarai)
I may add that Poompuhar is dated 20,000 years ago!
Reference and citation.
History Of Tamils by P.T Srinivasa Iyengar Page 301 to 321.