Captain Dataslate in the SM codex wrote:Rites of Battle (Aura): While a friendly <CHAPTER> CORE unit is within 6" of this model, each time a model in that unit makes an attack, re-roll a hit roll of 1.
MAKING ATTACKS section of the core rules wrote:Attacks are made using ranged or melee weapons. Attacks can be made one at a time, or, in some cases, you can roll for multiple attacks together. The following sequence is used to make attacks one at a time:
Since attacks are made one at a time, you can use the Rites of Battle (Aura) for each one of those attacks, as long as the attacking model meets the criteria of the Rites of Battle (Aura) rule.