Preheat the oven to 400° F. Generously spray a large baking sheet with non-stick cooking spray and set aside.
Chop your red onion, sweet potatoes, beets, and carrots into large chunks, about ½ inch in size. Slice your garlic cloves into thin slices.
Toss all of the chopped vegetables together and spread them out onto the prepared baking sheet.
Bake for 20 minutes.
After 20 minutes, remove the pan from the oven. Drizzle the oil and sprinkle the rosemary, thyme, sea salt, and pepper evenly over the vegetables and toss to coat. Continue baking for another 15-20 minutes or until vegetables are tender and easily pierced with a fork.