Preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper.
Toss the sweet potato rounds in olive oil, salt, and pepper. Arrange them in a single layer on the baking sheet and roast for 25-30 minutes, flipping halfway through, until they are crisp.
Remove the sweet potatoes from the oven and top with black beans and shredded cheese if using. Return to the oven for another 5 minutes until the cheese melts.
Once out of the oven, top with diced avocado, Greek yogurt, salsa, green onions, and cilantro.
Serve immediately and enjoy as a healthier version of classic nachos.