In small bowl, combine all olive salad ingredients; mix well. Set aside.
Spray broiler pan with nonstick cooking spray. Place mushroom slices on sprayed pan. In small bowl, combine oil and garlic powder; mix well. Brush half of oil mixture on mushrooms. Broil 4 to 6 inches from heat for 5 to 6 minutes or until tender, turning and brushing with remaining oil mixture once halfway through cooking. Remove mushrooms from pan.
Place rolls, cut side up, on broiler pan. Broil 4 to 6 inches from heat for 30 to 60 seconds or until golden brown.
Place cheese on bottom halves of rolls. Top with mushrooms, olive salad and tomato slices. Cover with top halves of rolls.