There are a lot of things resulting from a disappearance of Rome. When you want it to happen is up to you.
Arverni supremacy in Gaul, Seleucid domination of Ptolomaic Egypt without the Roman diplomats to turn them back, etc.
Egypt was largely propped up by Rome towards the end to ensure the grain shipments that were direly needed by Greece and Italy did not fall into enemy hands. Many people fail to take that facts like food shortages into account and this minor fact become largely ignored.
The Seleucids would probably cling on to dominance without Rome to butt heads with them over Greece and then Anatolia. It was after they lost Asia Minor that caused their manpower shortage that led to Parthians completely crushing their military power.
Dacians would continue to plague the Balkans and coalesce into a strong state, as would Gaul.
Romes intervention in Gaul stopped the Arverni taking over the entire place under their blasphemous (according to the druids) God King, the Verrix.
Carthage would dominate the Western Med, but there would be inter Senate struggles over the directions in which to expand like OTL.
The Barcids pushed for Iberian expansion while the Hannids (Hannos party) supported continued expansion into Africa. They became very bitter enemies.
Just some stuff to work with for you.