Preheat oven to 425°F.
In a large bowl, toss cauliflower florets with olive oil, smoked paprika, cumin, chili powder, salt, and pepper until well coated.
Spread cauliflower in a single layer on a baking sheet and roast for 20-25 minutes, or until lightly browned and tender.
While cauliflower is roasting, make the avocado crema by blending the avocado, sour cream, lime juice, and cilantro in a food processor or blender until smooth.
Warm tortillas in the oven or on a stovetop griddle.
To assemble tacos, place a spoonful of roasted cauliflower on each tortilla, then top with avocado crema and any desired toppings. Serve immediately. Enjoy your vegan roasted cauliflower tacos with avocado crema!