Short answers, pulled from the story.
The Roman Republic began in 509 BC, marking the start of a distinct architectural journey that would eventually span centuries. Before this date, Etruscan builders dominated the Italian landscape with their own unique styles and techniques.
Opus caementicium refers to Roman concrete which quickly supplanted brick as the primary building substance starting from the third or second century BC. The first use occurred in the town of Cosa sometime after 273 BC.
By the third century AD, eleven aqueducts sustained a population exceeding one million people. These systems included sedimentation tanks, sluices, and distribution tanks to regulate supply for cities and towns.
Cato the Elder built the oldest known example called the Basilica Porcia in Rome in 184 BC during his censorship. This structure contained interior colonnades dividing space into aisles with an apse at one end where magistrates sat on raised dais.
Quarries at Carrara were extensively developed for the capital from the reign of Augustus onward. Marble found rarely close to Rome until Augustus famously claimed he had left it made of stone after finding it brick.