Bring a large pot of generously salted water to a boil and cook pasta until very al dente, about 4 minutes. Drain and set aside.
In a large saucepan, melt butter over medium-low heat. Sprinkle in flour, then whisk together until a paste forms. Continue cooking, whisking constantly, until lightly golden, 3-5 minutes. Be careful not to let it burn.
Add milk to saucepan and whisk until smooth. Continue cooking until very thick, 3-5 minutes more. Reduce heat to low. Add cheese to sauce and stir to melt completely. Stir in half of the crumbled bacon, then season to taste with salt and pepper. Stir in cooked pasta, then remove from heat and set aside.
In a medium bowl, stir together crumbled cornbread, parsley, sage, rosemary, and remaining bacon. Transfer mac and cheese to a buttered 9x13” baking dish. Top with cornbread mixture, then bake until bubbly at the edges and golden on top, 20-25 minutes. Remove from oven and allow to cool at least 10 minutes before serving.