Heat oven to 400°F. Spray 9-inch square pan with cooking spray. Heat 10-inch nonstick skillet over medium-high heat. Cook sausage and bell pepper in skillet 7 to 9 minutes, stirring frequently, until sausage is no longer pink. Stir in mushrooms and pizza sauce. Keep warm over low heat.
Unroll dough in pan. Press in bottom and up side of pan, folding edge under to form crust. Sprinkle 1/2 cup of the cheese evenly in bottom of crust. Spoon hot sausage mixture over cheese. Top with remaining 1 cup cheese, the tomatoes and olives.
Bake 15 to 20 minutes or until crust is golden brown. Sprinkle with onions. Let stand 5 minutes. To serve, cut pizza into wedges with serrated knife.