Preheat the grill or grill pan over medium heat. Brush both sides of the zucchini slices with the oil and sprinkle with the salt and pepper. Grill until tender and slightly browned, about 4 minutes per side.
Spread 1/4 cup of the hummus over each piece of bread. Top with 3 slices of zucchini, 2 pieces of red pepper, 1/2 cup of the spinach, a few sliced onions, and 1 tablespoon of the mint. Roll each of them up and cut in half on a diagonal.