Crime in Rochester is practically non-existent, but there have been incidents.  Because of the size and conservatism of the city, visitors generally do not need to worry about crime as they would in larger cities like Chicago or D.C.  However, still follow the common sense safety precautions that you would anywhere else.  Your biggest safety concern will probably be protecting yourself from mosquitos carrying lyme disease in the summer, and watching your step on slippery sidewalks during the winter.