Romans killed Jesus in the name of Cesar. Romans bear the responsibility.
If one is a Christian one believes that all men, on account of their sins, bear the responsibility and are guilty of the death of the Lord.
If one is not a Christian then the only logical conclusion about guilt applies to the Roman officials and functionaries who carried out the crucifixion and the Sanhedrin officials and functionaries who threatened to incite a dangerous riot if the Romans did not comply.