Preheat oven to 425 degrees. Line a baking sheet with foil and place your chopped sweet potatoes on it. Pour avocado oil on top and toss to coat. Then sprinkle on salt, garlic powder and cumin and toss to coat.
Make sure they are in one even layer and roast for 15, then stir them about and flip them and roast for another 10-15 minutes or until nicely browned. Let cool slightly.
In a small bowl combine dairy free yogurt, lime juice, salt and garlic powder.
To assemble taco, take a piece of iceberg lettuce and top with some sweet potatoes, avocado pieces and drizzle on the lime crema.