On the other hand, the ethnic affiliations of crucifixion as a means of execution don't seem as secure as this. For one thing, in the famous discussion of Jewish methods of capital punishment in the Talmud (b. Sanh. 43a), "Jesus the Nazarene" (the translation is Peter Schäfer's [Jesus in the Talmud; Princeton University Press, 2007]), the text says a herald went out forty days prior to Jesus' execution to announce that Jesus was to be stoned and to seek out witnesses for his defense. When none were found, Jesus "was hanged" (tela’uhu), which Schäfer interprets as the post-mortem demonstration of Jesus' body after he had been stoned. But Joseph Fitzmyer argues that the root תלה [tlh], at least in the DSS, refers to crucifixion ("Crucifixion in Ancient Palestine, Qumran Literature, and the New Testament" [CBQ 40 (1978): 502–7]). I don't think b. Sanh. 43a provides any historical information about Jesus' death; rather, it reflects ongoing debate (between Jesus' followers and other Jews) about Jesus' significance. The world(s) in which Talmudic traditions were formed was/were also inhabited by Christians proclaiming a crucified Christ, and I'm impressed that, in the midst of this proclamation, b. Sanh. 43a accepts Jesus' execution at Jewish hands (regardless of the precise referent of תלה).
An additional complication comes from a very well-known story from Josephus, who describes the Hasmonean king/high priest Alexander Jannaeus as crucifying 800 Jews while he enjoyed a meal with his concubines, and as the men hung on their crosses he slaughtered their wives and children in front of them (Ant. 13.380). Josephus describes this as "the cruelest act of all" [πάντων ὠμότατον ἔργον; pantōn ōmotaton ergon), a phrase which may suggest the scandal of a Jew administering crucifixion as a means of executing people of his own nation. But the story remains as evidence that crucifixion could function as a Jewish means of execution. And, again, Fitzmyer finds similar phenomena in 4QpNah and in the Temple Scroll.
In all of this, I would suggest that we cannot read the gospels' Passion Narratives as mitigating Roman responsibility for Jesus' crucifixion and foisting blame on the Jews and/or the Jewish leaders. Rather, the gospels rather clearly portray Pilate's role in Jesus' trial and execution (whether or not we accept the historicity of their portrayal), and I would suggest the gospels even portray Jesus' fate as the result of the political posturing of Pilate and the Jewish authorities. The Jewish leaders wanted Jesus executed while Pilate made it clear that he wasn't simply their instrument to achieve their goals. Jesus' crucifixion served both the Jewish leadership's and the Romans' interests, but Pilate also made sure reinforce the political order over which he had been appointed by the emperor. After all, even the titulus Pilate had hung over Jesus' head announced not only the charge against Jesus but also, by why of parody, Judea's subjection to Rome.