Roasted Vegetable and Black Bean Tacos

Name: Roasted Vegetable and Black Bean Tacos
Ingredients: 1 small red onion, chopped; 1 poblano chile, seeded and chopped; 1 small zucchini, chopped; 1 sweet potato, peeled and chopped; 3 tablespoons olive oil; 1 1/2 teaspoons kosher salt; 1/2 teaspoon freshly ground black pepper; 1/2 teaspoon ground cumin; 1/2 teaspoon dried oregano; 1/4 teaspoon smoked paprika; Pinch of cayenne pepper; 1 (15 ounce) can black beans, drained and rinsed; 1 lime, juiced; 1/2 cup buttermilk; 1/4 cup sour cream; 8 corn tortillas; 1/2 cup crumbled cotija cheese