Preheat oven to 450 degrees.
Place chopped cauliflower in a gallon-size zip-top bag. In a small bowl, whisk together the margarine, hot sauce, and seasoning; add to the bag, zip and shake to coat all of the cauliflower. Scatter in a single layer on a baking sheet and roast for 15 minutes, stirring occasionally until browned and crisp on edges.
Meanwhile, heat a skillet on the stovetop. Once hot, place the corn tortillas one at a time, turning until browned and crisp in spots. This keeps the tortillas from tearing when they’re filled!
Assemble the tacos by laying out the tortillas, and top with the cauliflower, avocado, lettuce, jalapenos (optional), and onions. Spoon on some vegan ranch dressing and serve.