Preheat your oven to 375°F (190°C).
Toss the chopped root vegetables with olive oil, ground cinnamon, salt, and pepper in a large bowl until evenly coated.
Spread the coated vegetables in a single layer on a baking sheet and roast in the oven for about 25-30 minutes, or until tender and slightly caramelized.
While the vegetables roast, prepare the apple slices and set aside.
Once the vegetables are done, remove from oven and reduce the temperature to 350°F (175°C).
Layer the roasted vegetables evenly in the baking dish, then scatter the sliced apples over the top.
Mix the breadcrumbs with melted butter and chopped thyme, then sprinkle generously over the layered vegetables and apples.
Place the assembled casserole in the oven and bake for about 20-25 minutes, or until the topping is golden brown and bubbling along the edges.
Remove from oven, let it rest for 5 minutes so flavors meld, then serve warm and enjoy the hearty, aromatic fall flavors.