What is the Difference between byzantine architecture and roman architecture?

Early Christian Architecture was influenced a lot by Ancient Roman Architecture, which is characterized by repitition of arches. In this time, they actually converted old Roman buildings into religious structures, like the basilicas. On the other hand, Byzantine Architecture was inspired by Moorish Architecture because of the spread of Islam during that time. It is characterized by the addition of pointed elements, particularly in the dome. They introduce the onion dome, addition of pinnacles, turretts(not sure of the spelling), colorful mosaic murals, and introduction of colored buildings.

Early Christian architecture and early Byzantine architecture are one and the same, as the Byzantine (or Romans as they called themselves) were in fact the early christians. The Moors were not invented at the time. The Mosque archetype in Ottoman architecture (which in popular terms counts as "Moorish"), as well as the Rock Mosque in Jerusalem, draw partly their architectural language from the Hagia Sofia in Istanbul, which at the time of erection was the largest church of Christianity.