Preheat your oven to 375°F (190°C). Toss the chopped fall vegetables with a tablespoon of olive oil, salt, pepper, and thyme, then spread on a baking sheet. Roast for 20-25 minutes until tender and slightly caramelized.
Meanwhile, heat a skillet over medium heat with a tablespoon of olive oil. Add the minced garlic and cook until fragrant, about 30 seconds. Add the chicken pieces and cook until no longer pink, about 5-7 minutes. Season with salt and pepper to taste.
In a mixing bowl, combine the cooked rice, roasted vegetables, cooked chicken, and chicken broth. Stir gently to mix everything evenly and to allow the flavors to meld.
Transfer the mixture into a greased baking dish, spreading it out evenly. Sprinkle the shredded cheddar cheese over the top, followed by bread crumbs for a crispy topping.
Bake in the preheated oven for 20-25 minutes, until the cheese is melted and bubbly and the breadcrumb topping is golden brown.
Remove from the oven and let sit for a few minutes before serving. The casserole should be hot, with a crispy topping and warm, creamy interior filled with tender vegetables and chicken.
