Preheat oven to 375°F. Brush both sides of bread slices with oil and arrange on a large baking sheet. Bake until lightly browned and crisp, about 15 minutes, turning over halfway through. Let cool completely.
Preheat broiler to high; line a baking sheet with foil. Place peppers, skin side up, on baking sheet and broil until blackened, 10 to 12 minutes. Transfer to a paper bag, seal bag and allow peppers to steam for 10 minutes. Hold peppers under cold running water to remove skin. Pat dry with paper towels and chop.
Mix peppers, Parmesan, olives and parsley in a bowl. Spread each crostini with 1 Tbsp. of pepper mixture. Serve at room temperature.