Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
In a large bowl, toss the diced sweet potatoes with olive oil, salt, and black pepper. Spread them evenly on the prepared baking sheet.
Roast the sweet potatoes in the oven for 25-30 minutes, or until tender and slightly caramelized, stirring halfway through.
While the sweet potatoes are roasting, heat a grill pan or skillet over medium-high heat. Season the chicken breasts with salt and pepper.
Cook the chicken for about 6-7 minutes per side, or until fully cooked and no longer pink in the center. Brush the BBQ sauce over the chicken during the last few minutes of cooking.
Remove the chicken from the heat and let it rest for a few minutes before slicing it into strips.
In a large bowl, combine the roasted sweet potatoes, corn, black beans, and sliced chicken. Toss gently to mix.
Serve the mixture in bowls, topped with diced avocado, chopped cilantro, and a squeeze of lime juice.