Grape seeds found in ancient Sri Lanka may have been imported by Roman merchants. ISTOCK.COM/RINOCDZ
Literary sources and many archeological discoveries show that Rome and India had extensive trade relations, with Roman citizens settling in India and tigers and Asian elephants appearing in Roman zoos and art. The flow of Roman gold and silver to pay for spices and silk was large enough to alarm Roman officials in that it deflated the supply of specie to the Roman economy. The difficulty of transporting grapes from the Mediterranean though makes me inclined to think that there may have been local cultivation. After all, grapes were known to ancient India and are documented in its art and literature.
Sounds like there is plenty more to excavate. According to Wiki (I know) much of the ancient city is, well, sunken.