I personally wouldn't trade a P95 for a Rossi .357, a Taurus maybe but not a Rossi. I wasn't even aware that Rossi made a .357, but then I never look at Rossi revolvers. I had a Rossi .38 about 25 years ago and wasn't very impressed with it. The trigger pull was horrible on it. It may have just been a lemon, but I haven't cared to find out by getting another one just to find out.
If I were you, I'd look for somebody who had a Ruger .40 or .45 and wanted to trade for a 9mm. If you're interested in trading for the .357, I'd suggest shooting it and if you like how it shoots. If you're happy with it, trade him for it.