While there are plenty of robberies gone wrong, most murders in Rosario / Santa Fe are targeted and linked to narcotrafficking. If you stay around the main drags of Oroño, Puerto Norte, Fisherton etc you probably won't notice a thing and may even have a sensation of being safer than in CABA.
Every year judges, police, prosecutors, dealers, witnesses and even politicians or their families get knocked off.
Occasionally there are innocent bistanders, like the person in the carpark of City Center earlier this year and I also remember a while ago a restaurant got shot up by criminals thinking a rival dealer was inside. They killed nine people inside but he was not even there to begin with. Today you will find metal detectors at the entrance to some larger restaurants in Rosario as a precaution.
The common perception that I hear from those I know there is that in Santa Fe, crime and trafficking gets worse when there is a peronist government in charge of the province and security since they feel elements within those government appointments are more often than not linked to the trade.