Just a few thoughts...
Ultimately the ideal way to assess the risk associated with a supplier is by either a thorough food safety audit conducted by a qualified individual from your company or a 3rd party audit your company would conduct a physical audit for you. Food safety auditing guidelines should reflect your own food safety management system and the supplier must comply with relevant food safety legislation (I don't know what agency or agencies oversee this in Italy but in the U.S. it's primarily the FDA and USDA).
If this is an issue due to cost or a very large number of suppliers the next best steps (in my experience at least) would include:
- requesting 3rd party audit results (GFSI recognized schemes are at the top of that list)
- requesting regulatory inspection results
- having the supplier complete a thorough questionnaire
- having the customer send you a Letter of Guarantee
- research for the suppliers past history (internet search for recalls, withdrawals, labor issues, etc.)
The more information you can gather the more accurate your risk assessment will be (severity vs. likelihood). You should have a defined frequency as to your re-amassment of your suppliers in your food safety management plan (usually annually unless the supplier sells high risk product).
I hope that helps out a little bit.