When was the beginning of roman empire?

The beginning of the Roman Empire was in the 4th and 3rd century BC. In the 4th century BC and early 3rd century BC she expanded into central and southern Italy. She did not annex the peoples who leaved in these areas. Instead she turned into allies who had to pay a tribute and supply soldiers who fought in auxiliary troops which supported the Roman legions at their expense. Therefore, she established a form of Imperialism by indirect rule. At the end of the First Punic War 264 BC- 241 BC) she annexed Carthage's territories in western Sicily and soon afterwards she seized Sardinia and Corsica from Carthage. In the Second Punic War (218 BC-201 BC) she annexed Carthage's territories in southern Spain. At the end of Third Punic War (179 BC-176 BC) she destroyed Carthage and annexed her last territories in Tunisia and western Libya. In 176 BC she also annexed mainland Greece.

Further expansion of the Roman Empire occurred over the next two hundred years. The empire reached its greatest extent in 116 AD.