In a small bowl, stir together Greek yogurt, taco seasoning, and juice of 1/2 of the lime. Cover and place in the fridge or until ready to use.
Heat oil in a non-stick skillet over medium-low heat and toss sweet potato cubes in, cooking just until tender when pierced with a fork and edges are slightly browned. Salt and pepper lightly. Remove from heat.
In a bowl, toss together sweet potato cubes and black beans. Drizzle remaining lime juice over the top of the mixture. Salt and pepper lightly.
Spread a tablespoon of Greek yogurt mixture on the bottom of each wrap. Top with sweet potato mixture, tomatoes, avocado, and onions. Roll and tuck ends in. Cut in halves to serve.