Final answer:
The Roman building typology adopted for the new Christian churches in Rome after Constantine's conversion was the basilica. The basilica had a central nave with one aisle on each side and an apse at one end. This architectural form was appropriated by Christians for their worship.
Step-by-step explanation:
The Roman building typology that was adopted for the new Christian churches in Rome after Constantine's conversion was the basilica. The basilica was a common Roman building that served various civic and juridical purposes, such as law courts and senate meetings. It had a central nave with one aisle on each side and an apse at one end. Christians appropriated this architectural form for their worship, and many churches today still maintain the basic shape of a basilica.