Turn oven to broil. Toss broccoli with oil, salt, and pepper. Broil for four to six minutes, until broccoli begins to char a bit.

Add mushrooms, red pepper, salt, and pepper to the baking sheet. Toss to combine. Broil another eight to 10 minutes. Set aside.

In a small bowl, combine mayonnaise, sriracha sauce, salt, and pepper. Spread mixture on each slice of bread.

Top each slice with the vegetable mixture and shredded cheese.

Return bread slices to the broiler for just a few minutes, until cheese is melted and slightly browned.