Complex sentence: Indeed, Roman historian Plinius (V, 4,4) wrote about Tagaste, that was an important Christian center in Roman Africa, with a basilica and a Roman Catholic diocese that was the most important of Byzantine Numidia.
Split into simpler sentences: Indeed, Roman historian Plinius (V, 4,4) wrote about Tagaste, that was an important Christian center in Roman Africa. It had a basilica and a Roman Catholic diocese, the latter of which was the most important in Byzantine Numidia.