Heat oven to 425°F. On a large rimmed baking sheet, toss cauliflower with olive oil, chili powder, cumin, smoked paprika, garlic powder and salt until evenly coated, then spread in a single layer.
Roast 22-25 minutes, tossing halfway through, until florets are tender with browned edges.
Meanwhile, blend or mash the avocado, Greek yogurt and lime juice with a pinch of salt until smooth and pourable, adding a splash of water if needed, to make the crema.
Warm the tortillas in a dry skillet over medium heat, about 20 seconds per side.
Fill each tortilla with roasted cauliflower, drizzle with avocado crema and finish with cilantro; serve with lime wedges.
