Well, plenty of famous Roman figures made their fortunes by either starting wars themselves or leading campaigns (Caesar in Gaul, Pompey in the East [Syria and Judea primarily], just to name a couple although a bit later than your desired time line, a list I am sure others can add to) but there were other ways to make it big without starting a war. Under the mid-late Republic, I would argue that selfish (often financial) interests were the majority of motivation for Roman commanders. (IIRC Roman generals dying poor was such a rarity/marvel that they were often given a public burial at state expense). Historian R.H. Barrow (Slavery in the Roman Empire), put it far more succinctly than I can:

If war had passed, then there was no longer enslavement by war. But under the Republic, peace and good government were too often ousted by greed: the province was to be prey of its governor; rebellion was provoked, wholesale kidnapping tolerated, publicans and slave-dealers were given a free hand, if only the governor shared in its profits.

I don't think I'd go far as Barrow, but there is some truth to his sentiment, but lets just say that governors and other provincial authorities were a bit of a mixed bag so to speak. The primary issue being that even if they were god awful, there was no one with the force, authority, or desire to reign them in.

The lack of central authority and the autonomy of the generals (an autonomy which often manifested itself in selfish pursuits) was one of the key factors in the death of the Republic. Ch. Wirszubski, who wrote a wonderful book on Libertas as a political concept in the late Republic and early Principate, characterized this idea masterfully:

“As the ancients saw it, the Civil War was a struggle for dignitas [where we get our word for dignity, but better translated as prestige/reputation/honor in this context]: Pompey would tolerate no equal, Caesar would not brook a superior. Caesar himself admitted that he valued his dignitas more than his life, and that it was in defense of his dignitas that he appealed to armed force. Cicero was convinced that Caesar and Pompey alike strove for nothing else but power, and absolute power at that. Each of them fought for his own aggrandizement at the expense of the State. Thus dignitas, which was pursued without regard for other people’s libertas, proved to be a destructive factor in Roman public life.”

As far as the bigger picture goes, I think these "rouge" generals became more and more of a problem after the Fall of Carthage in the 2nd Punic War. Compared to the struggles and near complete failure of the 2nd Punic War, no rival in the Mediterranean could challenge Rome in the same way. Romans slowly began looking at one another, not just as social rivals to quarrel with, but as military threats to deal with.