The first source for the development of Roman theatre was the Etruscans.
It was a civilization that flourished northwest of Rome from 650 to 450 BCE.
They had a great emphasis on religious festivals.
The Ludi Romani (A Roman festival at which Greek drama was presented) was established by Tarquin the Elder, an Etruscan Roman Ruler.
Source: History of Theatre I Powerpoint (Roman Theatre)