why was there war between romanin and jews ?

Answer 1

Yes, there was. In about AD 70 the Jews revolted and there was a long war, the Romans being led by the future Emperor Valerian. The revolt led to the sack of the Temple in Jerusalem. The Jews last stand was at the desert stronghold of Masada.

Answer 2

Rome was an expansionist state that needed outside resources to maintain its large capital city - Rome. A route to great wealth and political influence for important politicians was to conquer new provinces that whose Natural resources could be developed to sustain the Imperial city and strengthen the empire. The Jews occupied an area that was rich in itself and which controlled major trade routes. As the regions of Palestine and Israel were occupied by disparate and mutually hostile groups the whole area looked like easy pickings for the Roman army. Although they did come to control it - and Roman control was maintained until the Muslim Conquests centuries later.(if the Byzantine Empire is accepted as the successor to the Roman Empire, which is reasonable) then the operation was successful. The major result though was to incorporate Jewish thinking and religious beliefs into the then global culture. It was this that facilitated the spread of Christianity.