Step 1: Prepare the vegetables
Preheat oven to 375°F (190°C). Toss the butternut squash, Brussels sprouts, and sweet potatoes with olive oil, salt, pepper, thyme, and rosemary. Spread on a baking sheet and roast for 20–25 minutes until tender.

Step 2: Brown the beef
While the vegetables roast, heat a large skillet over medium heat. Add ground beef, diced onion, and minced garlic. Cook until beef is browned and onions are translucent. Drain excess fat.

Step 3: Mix the casserole base
In a large bowl, combine the cooked beef mixture, roasted vegetables, cream of mushroom soup, and milk. Stir until well incorporated.

Step 4: Assemble the casserole
Transfer the mixture to a greased 9×13-inch baking dish. Sprinkle shredded cheddar and Parmesan evenly over the top.

Step 5: Bake
Bake uncovered for 25–30 minutes or until cheese is melted and bubbly, and the casserole is heated through.

Step 6: Serve
Let cool slightly before serving. Garnish with fresh herbs if desired.