score:3
That was true in the "early days" (basically the days of the Roman Republic). At that time, "Rome," (basically central Italy), was beset by Greek outposts (of so-called Magna Graecia) in southern Italy (as far north as modern Naples, at one time), Tarentum, and the Italian "boot." Also Carthaginian outposts in Lilybaem (Sicily), Caralis (Sardinia). And Carthage and its allies in North Africa weren't that far away. During the time of the Carthagian threat, a Roman Senator, Cato the Elder repeatedly exhorted his country to destroy Carthage: Carthago delenda est
By the end of the Second Punic War, Rome had neutralized the Carthaginian and Magna Graecia threats. They still had to worry about the balance of power in Greece itself, and whether the Macedonians, the Selucids, or the two in combination might threaten Italy from across the Adriatic. But four successful Macedonian wars (and one against the Selucids) took care of that threat.
Maybe there was a further threat from the Celts (Rome's ancient enemy) in Milan, and in Gaul. But Caesar's conquest of Gaul, and the earlier conquest of Spain and Milan had neutralized that threat.
By the time of the Caesars, Julius and Augustus, Rome had neutralized the immediate threats. It had no real need to expand further into Britain, Germany, or much beyond the shores of the eastern Mediterranean.
Upvote:7
Good question; have little time now for more than a couple of thoughts:
In the ancient world almost all states were, so to say, opportunistically expansionist. That is to say, almost no ruler or state ever passed an opportunity to take over the lands of a weak neighbour, either by direct force or by some form of intimidation. In that sense, Rome was not exceptionally aggressive - it was just the most successful.
Having said that, I must point out that the Empire did not embark upon new conquests after Augustus, with a few important but singular exceptions (Britain, Dacia, and the repeated attempts to quash Parthia). Under the Antonines a very self-conscious Roman Peace held which meant a purely defensive grand strategy.
In view of (2) I don't quite see how the conquests "doomed" Rome. (Though there is a point to be made here about Roman incursions being the consolidating factor for tribal confederations - a big complex issue).
There is at least one modern historian (V.N.Parfenov) who wrote an interesting monograph claiming that Augustus was indeed planning world conquest but backed out of it after the Teutoburg debacle. Of course this planning was predicated on a very faulty knowledge of geography, if it took place at all.