1Heat oven to 400°F. In 8-inch skillet, heat oil over medium-high heat. Add bell pepper and onion; cook 3 to 4 minutes, stirring frequently, until crisp-tender. Remove from heat. Stir in roast beef.
2Place pizza crusts on ungreased cookie sheet. Divide roast beef mixture evenly onto crusts. Sprinkle with cheese.
3Bake 8 to 10 minutes or until cheese is melted and crust is hot.