In spite of its repeted occurence, these precise things weren't that systematized, and even tended to be lowered in the late periods (Hellenistic and Roman), partially because of the Jewish presence.
Anyhow : if you manage to have a really early break of the Roman Empire, in the IInd century at the latest, then you'd have odds seeing a Jewish polity (or rather Jewish polities) popping around the eastern basin of the Mediterranean sea.
In 117, Jewish rebellions managed to hold Palestine, Cyprus, Cyrenaica and the coastal part of Egypt for a while (one of the reasons of Roman withdrawal of Persia), so having a Jewish rebellion in the wake of the collapse or withdrawal of Rome from Egypt isn't fat-fetched.
How long would it last, tough, is another question : Jewish communities (especially in Alexandria) were really frowned upon, and any popular rebellion in Egypt would be bound to have anti-juadic stances.