Questions regarding Azrael's warlord trait

The description reads:

"Brilliant Strategist: Once per battle, if your Warlord is on the battlefield you can re-roll a single hit roll, wound roll, damage roll or saving throw. In addition, if your army is Battle-forged, roll a D6 each time you use a Stratagem; on a 5+ you gain 1 Command Point"

Question 1: Does the reroll only count for Azzy or can it be used for anything in your army?

Question 2: Does "saving throw" include invulnerable saves as well?