Answer:
They would basically make an opening in the walls of the fort and swarm in. At times they would go over the walls. They also had their siege equipment for use. Depending on the constructions of the fort, they would use a battering ram, or fire to breach the walls. Sometimes diplomacy was used, at other times the defenders simply saw the Roman army and gave up. In still other instances a traitor would open the gates of the fort for the Romans to enter.