Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Dice the gold potato into uniform 1/2-inch cubes and trim the ends off the fresh green beans.
Mince the garlic cloves finely and strip the rosemary leaves from the stem, chopping them until very fine.
Cut the chicken breast into bite-sized pieces to ensure they cook at the same rate as the potatoes.
In a large mixing bowl, combine the chicken, potatoes, and green beans with the olive oil, garlic, rosemary, salt, and pepper.
Toss everything thoroughly until the ingredients are evenly coated in the oil and aromatics.
Spread the mixture in a single layer on the prepared baking sheet, ensuring no pieces are overlapping.
Roast for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the potatoes are crispy and fork-tender.