Preheat your oven to 400°F (200°C) and line a large rimmed sheet pan with parchment paper for easy cleanup.
Peel and dice the sweet potato into 1/2-inch cubes, and chop the red bell pepper into similar bite-sized pieces.
Cut the chicken breast into 1-inch chunks, ensuring they are uniform in size to cook evenly with the vegetables.
In a large mixing bowl, whisk together the extra virgin olive oil, balsamic vinegar, minced garlic, dried rosemary, sea salt, and black pepper.
Add the chicken, sweet potatoes, and bell peppers to the bowl and toss thoroughly until every piece is well-coated in the marinade.
Spread the mixture across the prepared sheet pan in a single layer, making sure not to crowd the pan so the vegetables roast rather than steam.
Roast in the center of the oven for 25 to 30 minutes, tossing the ingredients halfway through, until the chicken is cooked through and the sweet potatoes are tender and lightly caramelized.