Romans believed in many gods. They were believed to be all part of a family and were human-like except for the powers they were said to have had.
Maybe you’ll recognize several of their gods’ names: Saturn, Jupiter, Neptune, Mars, Venus, Mercury. Different gods were supposed to be in charge of different areas of life, so a person might sacrifice to the one he or she thought would most be able to help.
Capitoline Museums [CC BY 3.0]
When they conquered new people, the Romans just took on their gods as well, thinking maybe they could help them.
The Romans did have temples with statues, and priests were in charge of them so that they earned money from people coming and bringing money to the gods, and were fed by people bringing food to the gods as sacrifices. When emperors declared themselves to be gods, people had to worship them and sacrifice to them. When Christians refused, they were killed.
People would have small god statues in their homes. You can read in the Bible about the statue makers getting mad at Christians for teaching that theirs was only one, true God. It was bad for their business.
Christianity was made the official religion of the Roman Empire by the Emperor Constantine in the 4th century AD. It was probably one of the worst things that could have happened to the Church. Christianity lost its identity as one body that followed Christ and was becoming like him, and instead became something led by a man rather than led by God. Roman leaders weren’t following Christ or the Bible. It wasn’t Christianity, but it took on its name, giving Christianity a bad name instead of the reverent fear that surrounded Christians in the early church. It was the beginning of people using Christianity to seek power and money instead of seeking God and His righteousness.