Roppongi has, by Japanese standards, a slightly dangerous reputation and even makes it onto the US Department of State's Consular Information Sheet (http://travel.state.gov/t...), probably mostly for lack of anything else to warn about. The main hazard is drunken fights, which should be steered clear of as standard operating procedure for the police is to grab everybody in the vicinity and lock them up until things are sorted out, which may take its time. Some petty theft also occurs in crowded bars and clubs.
Be wary of hustlers on the streets, who will often try to talk foreigners into going to hideously overpriced bars or clubs--the extent of the overpricing may not even be apparent until you get the bill at 5:00AM. They can be quite aggressive, especially if they think you might be in the military, but they will leave you alone if you just keep walking and ignore them completely. Pretending to talk on your phone may help. Some clip joints send foreign female confederates into other bars to pick up clueless-looking targets, and an increasing number of them will spike your drink and then ravage your credit card while you're out cold. If you want to escape Roppongi with your wallet intact, stick to places on the lower level of buildings, preferably with a sizable crowd, and don't bring your credit card, as most of the legittimate places don't accept them anyway. Never go to a place suggested by someone you just met.
While that is the general perception of Roppongi, it is far less dangerous than the other major areas that cater to foreigners in Asia. It's not even the most dangerous place in Tokyo in terms of clubs hustling customers: that distinction goes to Kabukicho and its Yakuza-owned hostess bars. Some of the best clubs/bars require elevators to get into them. Remember that, it is slightly dangerous by Japanese standards, but Japanese crime standards are very different than those in much of the world. Roppongi is very safe, as long as you are not there during an earthquake. Many young women walk on the street alone late at night in complete comfort. The main danger is to your wallet.
