Tokyo Vice author Jake Adelstein called Roppongi a scum hole, and sure plenty of gaijins gravitate towards there, but it's very safe. There's even a great photo gallery there (Fuji Film building). The exhibition changes regularly and it's free. In fact, the most dangerous thing about Roppongi is that the station is located so far underground that you might die of old age while travelling on the many escalators to the surface!