Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the sweet potato and cut it into uniform 1/2-inch cubes to ensure they roast evenly.
In a large mixing bowl, combine the sweet potato cubes and the frozen mixed vegetables.
Drizzle the olive oil over the vegetables and sprinkle with garlic powder, dried oregano, sea salt, and black pepper.
Toss the mixture thoroughly until every piece is well-coated in oil and seasonings.
Spread the vegetables in a single layer on the prepared baking sheet, making sure not to crowd them so they develop a nice roast.
Roast for 20 to 25 minutes, tossing the vegetables halfway through, until the sweet potatoes are tender and golden brown.
While the vegetables roast, remove the skin from the rotisserie chicken and carve out 5 ounces of breast meat, slicing it into strips.
During the final 4 minutes of roasting, add the chicken strips to the baking sheet to gently warm them through.
Remove from the oven and serve immediately while the vegetables are hot and the flavors are vibrant.