You are admitting the Romans conquered Jerusalem and exiled millions of Jews into their Empire?
The province Palestine could never feed more than 300 000 inhabitants, the legends about millions of expelled Jews from Palestine do not have any scientific foundation.
Romans expelled maybe 20 000 Zealots (Terrorists, Trouble makers), but more than 90% of the inhabitants of Palestine remained where they lived from the time immemorial.
What happened to those Palestinians that never left their homeland?
Well, most of them became Christians. Christianity was in the very beginning a Hebrew Sect. Many Palestinian Christians later converted to Islam, that is why Jesus Christ and his mother are saints in Islam. Jesus was (according to Islam) a Muslim.
Today Jews are mainly descendants of non-Hebrew converts, like Berbers, Khazars or Slavs. The expelled Jewish Zealots married local women in Khazaria and other regions, proselytised pagans and founded the Jewish diaspora in the Middle Ages.
And most Palestinians are descendants of the Hebrews that accepted Christianity and later converted to Islam.
Some of them are still Christians.