Preheat the oven to 375 degrees. Coat the baking sheet with olive oil cooking spray.
Toss the sliced Brussels sprouts, mushrooms, tomatoes, cauliflower, and sliced onion on the baking sheet with some olive oil until evenly coated. Season the veggies with sea salt and freshly cracked pepper, crushed red pepper flakes, dried basil, and dried oregano, to taste. Add the sprigs of thyme to the top.
Place into the oven and roast for 8-10 minutes. Gently flip the vegetables with a spatula, then return to the oven to roast for another 8-10 minutes, or until the veggies are fork-tender and golden.
Remove from the oven then spoon into a serving bowl. Serve immediately. Enjoy.