Individuals killed Christ. It's as irrational to say "the Romans" killed Christ as to say "the Jews" killed Christ. Individuals of various ethnicities participated, but they remained individuals.
In any event, your position is irrational if you accept the notion of military or governmental action. It's true that D-Day, for example, was the work of individuals but most people accept the concept that the Allies(as a group)landed at Normandy. Hence, individual Syrian mercenaries may have scourged Jesus and pounded the nails but they did so, as soldiers do, while "Following Orders" of the Roman Governor who spoke for the Roman Empire.
It is the Romans who killed Christ in the sense that I've outlined, a sense that most people would understand.