There is indirect evidence that organized crime was rampant actually. If not rampant, enough for the Roman Senate to outlaw collegia, which were contributing to organized violence against politicians in Rome in 64 BC. There was a figure during the Triumvirate named Clodius that reversed this ban during his Tribunate in 58 and some accounts have him acting as somewhat of a gang leader. For example, when consuls Pompey and Gabinus protest his critique of their policies in the east he has his supporters beat them up and smash their fasces, the symbol of their power. He actually ends up dying in a "gang fight" against one of his political opponents Milo.

I actually just wrote a paper on how organized crime as we know it today probably wasn't seen as "crime" back then but the actual power structure of how someone obtained security and legal representation, at least in the Republic. It was basically seen as legitimate. There was no police force, and many laws were about how you should deal with thieves yourself (how you should go about killing them) rather than bringing them to court, giving them due process, all those modern inventions. So most people subscribed to a patron who gave them legal and presumably physical protection as well.

If anyone thinks this is incorrect, please correct me, as I am not an expert.