Preheat the oven to 420 degrees. Add the diced peppers, onions, and shallot to a bowl. Drizzle with oil and season with salt and pepper. Toss to coat. Pour the vegetables onto a parchment-lined baking sheet. Roast for 25-35 minutes until vegetables start to caramelize. Set aside to cool.
Half of the vegetables will be used on the pizza. Refrigerate the remaining roasted vegetables for another use.
Increase oven temperature to 500 degrees. On a sheet pan lightly brushed with oil, shape the pizza dough into a rectangle. Spread a layer of pesto on the dough. Top the pesto with a layer of mozzarella cheese slices. Next, top with the vegetables and sliced black olives.
Bake the pizza for 10-12 minutes until crust is crispy and pizza is lightly browned around the edges. Cut into squares and enjoy!