Rome has changed greatly during the years shown on the time line. About how Many years passed between the republic being established and Rome having its first emperor

482 years

Explanation:

From the timeline above, we see that Rome was established as a Republic in the year: 509 BC.

Octavian also known as Augustus, became the first emperor of Rome in the year 27 BC thereby changing Rome to an empire.

The number of years between these dates is therefore:

= 509 - 27

= 482 years