Place chopped sweet potatoes and onion into a large mixing bowl. Add coconut oil (if you are avoiding oil and remaining fat-free, you can leave this out - it tastes just as great without it), thyme, cumin, minced garlic, sea salt, and black pepper. Mix everything until it’s evenly spread. Layer onto a baking sheet. Roast for about 25 minutes or until the edges start to brown. Remove from the oven and allow it to cool for about 15 minutes.
Add vegetable broth to a high-speed blender. Next, add the roasted vegetables and blend until smooth. Add more sea salt and black pepper if needed.