Heat olive oil over medium-high heat in a large nonstick pan. Add red bell pepper and sweet onion and cook until crisp-tender.
Roll prepared pizza dough into a rectangle that’s about 9 to 10 inches long on parchment paper.
Sprinkle shredded mozzarella on dough. Arrange mini pepperoni slices evenly across dough and top with red bell pepper and sweet onion.
Roll dough up starting on a long side. Tuck the ends under and pinch to seal the seam.
Set Air Fryer to 350 degrees for 15 minutes. Let heat for 2 minutes. When time is down to 13 minutes, place stromboli seam side down in Air Fryer. Spray top with cooking spray and sprinkle garlic powder on top.
Cook for remaining 13 minutes. Slice and serve with pizza sauce.