Preheat the oven to 450°F. Line a sheet pan with foil. Toss the oil and chickpeas together on the prepared sheet pan. Roast for 30 minutes, until the chickpeas are crispy. While they roast, make the spice mixture, if using, by combining the paprika, garlic powder, and cayenne.
In a jar or small bowl, combine the mustard, vinegar, lemon juice, mayonnaise, nutritional yeast, olive oil, a few pinches each of salt and pepper, and 1 tablespoon water. Cover the jar and shake vigorously to combine, or whisk the ingredients together thoroughly in the bowl. Add more water, if needed, to thin the dressing to your desired consistency.
Arrange an oven rack in the top position and preheat the broiler. Place romaine halves on a sheet pan. Brush each one generously with a few swipes of Caesar Dressing and sprinkle with a little Parmesan. Broil until the tops look shriveled and browned but not burned, about 5 minutes. Transfer the romaine to a platter. Top with crispy chickpeas, red onion, herbs, if using, and drizzle everything with more dressing.
