Preheat the oven to 375 degrees. Coat a glass baking dish with cooking spray.
Toss the diced potatoes, carrots, and onion together with the olive oil in the prepared baking dish then season with sea salt, freshly cracked pepper, and garlic powder, to taste.
Place into the oven and roast for 30 minutes. Remove from the oven then add the broccoli and stir together. Roast for an additional 15 minutes or until the vegetables are fork-tender. Taste and re-season with sea salt freshly cracked pepper, and garlic powder, to taste, if needed. Serve and enjoy.