Heat oven to 350°F. Spray large cookie sheet with cooking spray. Unroll dough on cookie sheet; starting at center, press dough into 15x10-inch rectangle. Place roast beef on dough in even layer to within 1 inch of edges. Top with 3/4 cup of the cheese.
In 10-inch skillet, heat oil over medium-high heat. Cook onion and bell pepper in oil 5 minutes, stirring frequently. Spread mixture evenly on top of cheese. Starting on 15-inch side, roll dough tightly. Pinch edges of dough to seal; turn ends under. Arrange roll diagonally on cookie sheet, seam side down.
Bake 30 to 35 minutes or until golden brown, topping with remaining 1/2 cup cheese during last 5 minutes of bake time. Cool 5 minutes. Cut into 12 slices.