> Flat bread must have been the first kind of bread: you just mix flour and water and heat it.
And keep some "old dough" for starting the next batch. The general concept of a "sourdough starter" arises from that. This was pretty much the only form of bread yeast until 1850 or so https://en.wikipedia.org/wiki/Baker%27s_yeast#History
And have a look at the wood-fired bead ovens in Pompeii. They're quite similar to the Pizza ovens down the road in Napoli. It's likely that the Romans made similar dishes: flatbread with cheese, meat, sauce and herbs baked on top.
In some districts in Rome, they had large apartment blocks (insualae) several levels high, and fire was forbidden, so people had to buy food on the streets.
From wiki: The insulae could be built up to nine storeys, before Augustus introduced a height limit of about 68 feet. Later, this was reduced further, to about 58 feet
But also the technique of leavening using natural yeast has been known for thousands of years; it pre-dates the Romans, who definitely used it in their regular bread.
I'd say that running a bakery under those conditions: i.e. would always be yeast around and there is no refrigeration, so for any given dough it's a question of when, not if, a given piece of dough will start to rise.
And keep some "old dough" for starting the next batch. The general concept of a "sourdough starter" arises from that. This was pretty much the only form of bread yeast until 1850 or so https://en.wikipedia.org/wiki/Baker%27s_yeast#History
And have a look at the wood-fired bead ovens in Pompeii. They're quite similar to the Pizza ovens down the road in Napoli. It's likely that the Romans made similar dishes: flatbread with cheese, meat, sauce and herbs baked on top.
But not tomatoes yet, until 1600s or later, after the Columbian exchange https://en.wikipedia.org/wiki/Columbian_exchange