We actually have a primary source for this- Flavius Josephus. Originally a leader of the Jewish forces, he was captured by Vespasian in 67AD and retained as a translator of sorts for Vespasian and his son Titus, the latter of whom commanded the siege of Jerusalem. Josephus was there too, with direct access to the Roman commander and yet also an intimate understanding of the defenders- his own people. He would later write about it in his History of the Jewish War (often just called War), translations of which should be fairly easy to track down.

Like a lot of primary Roman era sources you do need to be conscious of the potential for bias in the author- Josephus was writing under Flavian patronage- but he at least makes claim at presenting a balanced accounting and for anyone interested in the siege it's hard to top the account of a historian who experienced it first hand.