[BenLurkin]

The Republic was expanding its sphere of influence for centuries, but there was no empire until founded by Augustus in 27 BC.

[SunkenCiv]

That's an interesting point of view, it just happens to be unshared by the overwhelming majority of historians, and it clearly not based on anything much.

[Cronos]

Not really, Ben -- prior to 27 BC there was a Roman Empire. It was run by and established by the Republic. It started, as SC had said, right from the conquest of the other Latin cities by Roma.

Having done that, they created what is arguably an Empire

The term empire does mean a set of captive nations ruled by another nation -- it doesn't matter what that ruler nation's government is.

Note that also there were Emperors (or specifically Imperators i.e. Military dictators/commanders in chief) right from the early days of the Republic.

Augustus didn't establish the Empire, he established the position of Princep (first among equals) that was kept until Diocletian started the Dominate period