Tomatoes are not indigenous to Europe, they are indigenous to South America. Therefore the Romans did not eat pizza. Nothing in any ancient source can be a reference to pizza, because one of the key ingredients to make pizza did not exist in Europe. The Roman bread made around Campania bears a geometric similarity to pizza, in that it is baked round and then cut into slices as you can see from this bread from Herculaneum, preserved by the eruption of Mt. Vesuvius and this loaf from Pompeii, but it wasn't pizza. They might have put some toppings on it - Aeneas puts berries on his stale bread (the 'table') before eating it - but in Pompeii frescoes the bread is shown without any garnish or toppings.

If you want to know what food in Italy was like before the introduction of the tomato, see What was Italian cuisine like before tomatoes? with answers by /u/Grombrindal18 and /u/jschooltiger.