HEAT oil in large skillet on medium-high heat. Add vegetables; cook and stir 5 to 6 min. or until crisp-tender. Remove from skillet; cover to keep warm.
ADD meat; cook 1 to 2 min. or until browned, stirring occasionally. Add pepper mixture and steak sauce; mix lightly. Cook 3 to 4 min. or until meat is done, stirring occasionally.
FILL rolls with meat mixture and cheese.