Preheat the oven to 400 degrees F.
Cut the cauliflower into 1/2-inch thick slices. Break up any larger pieces of cauliflower.
In a large bowl, whisk together the olive oil, chopped chipotles and sauce, lime juice, cumin, oregano, garlic powder, onion powder, salt and black pepper.
Stir the cauliflower into the marinade.
Spread the cauliflower across a sheet pan in a single layer. Roast for 25-30 minutes, flipping halfway through cooking, until browned at the edges.
While the cauliflower is roasting, make the avocado crema. Combine the avocado, yogurt, lime juice, water, cilantro, salt and pepper in the bowl of a food processor. Puree until smooth.
To assemble the tacos, fill the warmed tortillas with roasted cauliflower, black beans, radishes and cilantro. Generously dollop on the avocado crema. Serve with lime wedges on the side.