The Romans were many things including meticulous record keepers. They were very clear about expelling and/or enslaving most Judean Jews (as opposed to those already in diaspora communities) after the Bar Kochba rebellion which ended in 133 CE. For 100 years before then, the Romans had pursued a policy of colonialization of Greek and Hellenized Syrian migration into Judea. After 133 the Romans implemented a policy of deJudaizing Judea. They renamed the province Palestine after the extinct Phillistines and renamed Jerusalem Aeolia Capitolina, building a pagan sanctuatry on Mt. Moriah.
There were a few more rebellions, the last one around 630 during the last Persian-Byzantine war. However, by that point, a majority of the population in Byzantine occupied Judea was Greek-Christian. The 1/3 of Palestinians whose families actually from the are actually from Palestine (as opposed to Arab immigrants from (1890-1947) are decended from converts (voluntary and foreced) as well as of Arabs who settled in land grants given to veterans by the Abbasid Fatamid Caliphates.