The early Christians of Jerusalem, as I've already discussed, were seen as a Jewish sect. Paul came to the Jerusalem Council and argued to allow Gentiles (non-Jews) to become Christians. As more gentiles joined the fold, many true Jews were upset, and they were angry with some of the teachings of the Christians. Remember the martyrdom of Stephen. Following the Stephen's murder, the Christians fled Jerusalem and spread the Gospel throughout Judea and into Asia-Minor (Turkey) and North Africa, as well as throughout the Roman Empire.
The Romans worshipped and sacrificed to many gods, while the Christians denied the existance of any god, but the one true God. The Christians practiced Communion in secret, and rumors developed about Christians being cannibals (eating the body and drinking blood). Christians also stood against the status quo and were revolutionary with their teachings such as Love your enemies, and that slaves could be rewarded equally with the rich and the nobles in Christ's service. In fact in Galatians 3:28, Paul stated that there was neither Jew nor Greek, neither "slave nor free, there is neither male nor female." This type of talk was very offensive to the castes of the Romans.
The Romans were also fed up with the Jewish zealots and revolts throughout Judea that had been occurring for almost a hundred years. Around 50 A.D. during a Passover ceremony, a Roman guard "mooned" the Jewish elect and chaos and rioting resulted. When all was over, nearly 30,000 Jews were killed. Eventually Jewish zealots attacked Roman outposts and Nero sent General Vespasian to end the problem. Soon after, Vespasian was crowned the Roman emperor. On August 5, 70 A.D. the Romans conquered Jerusalem and burned the temple mount to the ground. Following this tragedy the Jewish leaders of the Diaspora (the time of scattering througout all the lands of the world), began to exclude other groups, such as the Christians. Timothy Paul Jones, a modern scholar and minister, writes that by "90 A.D. the weekly synagogue prayers included a curse against" the Christians.
Emperor Domitian (son of Vespasian) continued persecuting all Jewish groups, including the Christians. Then Emperor Trajan also persecuted the Christians. Christians were considered outlaws and criminals and were hunted down, killed in the arenas, burned, and crucified. Many of the early Christians began to believe that they could earn their way to Heaven by dying as martyrs, though most of the leaders of the Church taught against this early "heresy." By the mid-100s, many Christian leaders became known as apologists, as they argued to prove that Christians were not criminals or outlaws.
The Christian God was different from the Roman ones. He was a personal savior. He had suffered and died. He understood human suffering and loss. Despite all the persecution and violence, Christianity continued to grow throughout the Roman Empire, as people sought this personal relationship with a loving God. It has been said the Church grows more when it is persecuted. This may be true, it certainly was in the Roman days.
God did not promise anything in this life, but peace and joy of the soul in relationship with Him. To the early Christians, that was enough.