Josephus' passages about Jesus are widely acknowledged as later Christian interpolations into his text.
Actually one of them (the James passage) is widely acknowledged as genuine. The other is disputed however, many historians accept at least parts of it as genuine.
The 2nd-century Roman authors actually do nothing more than echoing contemporary Christian beliefs and legends -- they are secondary to the Christian Jesus stories (if not to the written Gospels).
This is a liberal claim. However, there is nothing in the text of the Roman historian Tacitus (Ad 115 Annals 15.44. ) to indicate anything other than an actual historical Roman related (Pilate) event being recorded.
"But not all the relief that could come from man, not all the bounties that the prince could bestow, nor all the atonements which could be presented to the gods, availed to relieve Nero from the infamy of being believed to have ordered the conflagration, the fire of Rome. Hence to suppress the rumor, he falsely charged with the guilt, and punished Christians, who were hated for their enormities. Christus, the founder of the name, was put to death by Pontius Pilate, procurator of Judea in the reign of Tiberius: but the pernicious superstition, repressed for a time broke out again, not only through Judea, where the mischief originated, but through the city of Rome also, where all things hideous and shameful from every part of the world find their center and become popular. Accordingly, an arrest was first made of all who pleaded guilty; then, upon their information, an immense multitude was convicted, not so much of the crime of firing the city, as of hatred against mankind."
