Preheat the oven to 400 degrees. Line a baking sheet with parchment paper and set aside. In a large bowl combine the shrimp, olive oil, ½ teaspoon salt, 1/4 teaspoon chili powder, and pepper. Toss to coat. Pour into the baking sheet. Roast until pink and firm (about 6-8 minutes). Meanwhile, in a blender combine the sour cream, Chipotle pepper, garlic clove, lime juice, and remaining salt until smooth. Remove the shrimp from the oven and toss with the corn, black beans, jalapeno, 1/4 teaspoon chili powder, and cumin. Spoon the shrimp filling into the avocado halves and top with the sour cream sauce.