Preheat the oven to 425°F. Add the 3 large sweet potatoes peeled and cut into 1-inch cubes to a large baking sheet. Toss with 1 1/2 tablespoons olive oil or avocado oil, 1/2 teaspoon salt, 1/2 teaspoon black pepper, 1/2 teaspoon paprika, and 1/2 teaspoon garlic powder. Spread into an even layer and roast for 25 to 30 minutes, flipping halfway through, until tender and lightly browned.
Meanwhile, cook the 2 pounds lean ground beef in a large skillet over medium-high heat, breaking it apart as it cooks. Once browned and cooked through, drain any excess grease. Add the 1 packet taco seasoning and prepare according to the package directions.
Add the 2 cups corn to a large skillet over medium-high heat. Cook for about 5 to 7 minutes, stirring occasionally, until lightly charred. Remove from the heat and let cool for a few minutes.
Add the charred corn to a medium bowl with the 1/2 cup finely diced red onion, 1/4 cup chopped fresh cilantro, 1/3 cup sour cream, 1/3 cup mayonnaise, 1/4 cup crumbled cotija cheese, Juice of 1 lime, and 1/2 teaspoon Tajín or elote seasoning. Stir until well combined.
Divide the roasted sweet potatoes among 6 bowls. Top with the taco meat and street corn mixture. Garnish with extra cotija, cilantro, Tajín, and fresh lime, if desired.