Jesus was one of dozens around that time that people claiming they were the Moshiach. Many Jewish groups were eager for he overthrow of the Romans, and Roman authorities to some level were aware that the belief in the Moshiach would mean the overthrow of Roman power. Any claim that someone is the messiah is a claim to kingship, it's meant to be a continuation of the line of David and its rule into a divine Jewish age.
How any individual Romans would have seen that, we don't have much. I mean, the earliest representation we have from what we presume is an ordinary Roman person is graffiti mocking the whole concept (Jesus is portrayed with a donkey's head), but obviously enough would convert over the centuries to make it a power.
strictly speaking if they would riot etc then in theory what choice did the romans etc ?
They had a lot of other options, which they used repeatedly in the many riots that happened. Jesus wasn't unique in any of this, he's unique in that those who continued on after him developing enough of a following to separate out of Judaism in the centuries that followed, while the others developed back into it. We also no evidence of the time that any such riot was going to occur around Jesus - remember that there is no historical evidence of any thing in the Pontius Pilate court scene ever happening to anyone. The idea of some sort of annual tradition to release a prisoner, not seen anywhere else. The Jewish authorities at the time did not have the kind of authority or link with Roman powers that are portrayed and Rome had a lot of options for dealing with it. We see their use of it all over their empire.
The bible clearly states that the Romans, Pontius Pilate specifically, did not see Jesus Christ as a threat but the Jews (Saduccess and Pharisees) did and so, to pacify them under threat of rioting (and in order to fulfil the prophecy of the Messiah), He was crucified.
The Pharisees and Sadducees were religiously focused political groups that had fought each other for political and religious power for well over a century before Jesus came in. Their fighting is a big part of how Rome gained control in the way it did. Equating them to the Jewish people at the time is like saying Evangelical US Republicans is the same as all American Christians. They also supported various different potential messiahs during Roman rule (within some Jewish traditions, there are potential messiahs in every generation and there have been far more potentials that have fallen over the centuries).
Rome managed to handle all the other riots and rebellions without any mention of some tradition of sacrificing someone for the Jewish people's whims. Rome was really good at that for most of its empire.
plus how can anyone believe in Christianity, when the majority is copyed from pagan influences ? if Christianity was truly its own religion then why did the leaders of the day choose to include pagan rituals and believes etc
As others said, Christianity comes from Judaism. It developed enough and differently enough to splinter off of it.
The entire concept of pagan to mean a religious belief or rituals is a Christian concept. It was not something any Roman at the time of Jesus would have viewed themselves or their rituals as. Pagan to mean a belief system only shows up starting in the 4th century CE by Christian writers, after Christians developed out of Judaism and developed enough power to make an us vs them (pagans and at times Jewish people) dynamic in their writing. The polytheists of the time had various other language to discuss themselves, just as many do today. Pagan is simply an umbrella term created by Christians to cover (and largely homogenise) many different systems of belief (at the time of Jesus, religion had very different meaning, that's how we have secular and religious priests for quite a while).
The idea that Christianity just copied pagans is a Victorian myth by European folklorists and linguists who wanted to erase the Jewish history of Christianity and replace it with their ideas of European paganism that they largely made up to fill the gaps in the record and replace what they didn't like. I mean, we all hear how Christianity stole the dating of Yule to convert pagans - that first comes from Victorian writers. The remaining historical records show Yule was used to convert pagans - several centuries after it had started being celebrated. King Hakon of Norway, after converting to Christianity, moved the date of Yule back three weeks to line up with Christmas, which under the Julian calendar could line up with the winter solstice. Celebrating Yule on the winter solstice is a Christianised version. Most of what we have left is the Christianised version due to the limited resources left, and people develop things from that as people always do. That doesn't make modern paganism not a 'true religion', it just makes it one of many faith systems that have complicated roots.