Preheat oven to 350 degrees Fahrenheit and grease a 9.5-inch baking dish with olive oil. Set aside.
In a large bowl combine sweet potato, parsnips, flour, sea salt, pepper, nutmeg, red pepper flakes, and dried thyme. Stir to combine.
Spread a layer of Condensed Cauliflower Soup on the bottom on baking dish. Add one layer of sliced sweet potato and parsnips, overlapping slightly, to dish. Sprinkle with parmesan cheese and a drizzle of Condensed Cauliflower Soup. Repeat with the remainder of the sweet potatoes and parsnips, parmesan cheese, and Condensed Cauliflower Soup. Sprinkle the top of the gratin with gruyere cheese.
Cover baking dish with foil and bake for 40 minutes. Remove oil, return to the oven, and cook an additional 30 minutes, or until gruyere cheese is bubbly and browned and vegetables are fork tender.
Remove from oven, cover with foil, and let sit 20 minutes.
Garnish with fresh thyme and enjoy!