Please be careful..no fanny packs, no easy access purse or wallets in side or back pockets etc.....I was in Rome for last few weeks and did see one pickpocket theft on the metro (Colosseo).
The thing is: I had watched a few YouTube videos about pickpockets in Rome and these videos seemed exaggerated, or almost staged, and in the realm of clickbait.
I was wrong.
Saw one that was almost exactly as filmed on a video I saw: Group of young women jump a head of an elderly group in the line into the metro car; they take a place at the door, occupying space to make entry difficult; bump into an elderly lady (who spoke only German); she passes them with difficulty to get into the car, and when the signal sounds that doors are going to close, they rush out of the metro car and the doors are now closed; they walk away ; the train goes to the next station.
They elderly women realized what happened too late, started banging on the door to open it, pointing at the young women to no avail.
She fell on the floor and started crying, being comforted by her group and a monk who happened to be on board. My German is not good, but she seemed to say they had taken everything.
Please be paranoid on the metro and trains and crowded areas.....I put my bag in front of me, hands on the opening, and all important documents I had in a carrying sleeve underneath my sweater .
The salaries for most people in Rome are surprisingly small (google: Generazione mille, not the film but the meaning) and tourists carry a good amount of money/credit cards/jewelry etc when compared to citizens of Rome. Further if you do not speak Italian and are lost in a strange city, you are an easy target.
The only thing you should be doing on the metro / bus is paying attention to your surrounding...no iPhone, no maps , no looking at documents etc etc