Sprinkle a pork sirloin roast with seasonings, and roast it at 400 degrees Fahrenheit for 30 minutes per pound. The meat is cooked when a meat thermometer reads 155 degrees Fahrenheit. Cook vegetables with the roast for extra flavor.
Preheat the oven to 400 degrees Fahrenheit. Spray a large roasting pan with cooking spray. Remove fat from the pork sirloin roast, and spray the roast with cooking spray or rub lightly with oil. Sprinkle 1/2 teaspoon of salt, 1/8 teaspoon of pepper and 1 teaspoon of rosemary on the roast. Place the roast into the center of the roasting pan.
In a large bowl, mix 2 pounds of baby carrots with a large sweet onion that has been cut into wedges. Add 1/2 teaspoon of garlic powder, 1 teaspoon of rosemary, 1/2 teaspoon of salt and 1/8 teaspoon of pepper. Stir until the vegetables are evenly coated with spices. Place the vegetables into the roasting pan around the pork roast. Spray the vegetables lightly with cooking spray.
Roast uncovered for 30 minutes per pound of roast. Remove the roast from the oven when the meat thermometer reads 155 degrees Fahrenheit. Cover with foil, and allow the roast to rest for 10 minutes or until the meat thermometer reads 160 degrees Fahrenheit. Serve the pork with the vegetables.