The city of Rome itself has tremendous environmental advantages, which made it easier for Rome to become an important city. Rome is located at the first place that people can easily cross the Tiber river, so it is the natural location of the main north-south road in Italy. The reason you can cross the Tiber at Rome is that there is an island in the river there (this is the same as at Paris, and many other cities). Probably the first Romans made a lot of profit from charging people to let them use the island to cross the river – charging tolls.
There are also big salt flats near the city. Because salt was so valuable in the ancient world for preserving meat and fish, selling the salt made Romans rich. Also the riverboats going up and down the Tiber, from east to west and back again, could stop at Rome.
As the Romans expanded their empire, they encountered many different environments. There were mountains, wetlands, forests, and everything else. The great variety of environments helped the Romans get lots of different food and materials. They could get tin from England, and wood from Germany, and cotton from Egypt, and silver from Spain.
The Romans also had the advantage of a good climate. During most of the time of the Roman Empire, Europe and the Mediterranean were unusually warm, about as warm as they are right now. That weather seems to have been good for Roman farming. The Romans brought Mediterranean crops like wine grapes and olives much further north than they normally grew.
But during the 200s AD, the weather got cooler. The cooler weather forced wine and olive growers to move south. It may even have made it harder to grow wheat and barley. The cooler weather made it harder to heat houses in the north. This may have helped cause problems for the Romans. The cold weather may have encouraged the Germans and the Sassanians to invade the Roman Empire. It may have encouraged many people to revolt inside the Empire as well. The fall of Rome in the 400s AD may also be related to this cooler climate, which lasted into the Early Middle Ages, until the 600s AD.