Preheat oven to 375°F (190°C).
In a small bowl, combine rosemary, thyme, garlic powder, onion powder, salt, and pepper.
Rub the roast with olive oil, then coat evenly with the herb mixture.
Place the roast in a large roasting pan.
In a separate bowl, toss the carrots, parsnips, potatoes, and onion with olive oil, salt, and pepper.
Arrange the vegetables around the roast in the pan.
Roast for 1 hour 30 minutes, or until the internal temperature reaches your preferred doneness.
Let the roast rest for 10 minutes, then slice and serve with the roasted vegetables.