Preheat oven to 425 degrees and line a baking sheet with foil.
In a large bowl combine cauliflower, olive oil, garlic powder, chili powder, pepper and 1/4 cup of buffalo sauce. Stir to combine. Spread evenly on baking sheet and cook for 20 minutes, flipping halfway.*
Five minutes before the cauliflower is done cooking, heat up the remaining buffalo sauce in a saucepan or in the microwave.
Remove cauliflower from the oven and place it back in the bowl. Add remaining heated buffalo sauce and stir to combine.
To assemble tacos, load each tortilla with romaine, avocado and cauliflower. Drizzle with ranch and top with cilantro or green onions.