Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper.
Wash and dice the gold potatoes into 1-inch cubes, and trim the ends off the green beans.
Slice the chicken breast into bite-sized pieces of uniform size for even cooking.
In a large mixing bowl, whisk together the olive oil, lemon juice, dried oregano, garlic powder, sea salt, and black pepper.
Add the chicken, potatoes, and green beans to the bowl and toss thoroughly until every piece is well coated in the herb marinade.
Spread the mixture in a single layer across the prepared sheet pan, ensuring items are not overcrowded so they roast rather than steam.
Place in the oven and roast for 20 to 25 minutes, or until the chicken is cooked through and the potatoes are fork-tender and golden.
Remove from the oven and sprinkle with finely chopped fresh rosemary before serving warm.