Heat oven to 400°. Grease 12-inch pizza pan with shortening. Unroll dough; place in pan. Bake 6 to 8 minutes or until crust begins to dry.
While crust is baking, spray 10-inch nonstick skillet with cooking spray; heat over medium-high heat. Cook frozen bell pepper mixture in skillet 4 to 5 minutes, stirring frequently, until crisp-tender.
Spread Dijon-mayonnaise blend over partially baked crust. Top with roast beef, bell pepper mixture and cheese. Bake 15 to 20 minutes longer or until crust is golden brown and cheese is melted. Cut into wedge to serve.