Preheat oven to 400 degrees F. Lightly oil a 9 x 13 baking dish or coat with nonstick spray.
Spread bread cubes in a single layer on a baking sheet. Place into oven and bake until crisp and golden, about 10-13 minutes; set aside.
Heat olive oil in a large cast iron skillet over medium heat. Add sausage and cook until browned, about 5-8 minutes, making sure to crumble the sausage as it cooks. Transfer sausage to a paper towel-lined plate.
Melt butter in the skillet. Add garlic, onion and celery, and cook, stirring occasionally, until tender, about 4-5 minutes. Stir in parsley, sage, thyme and rosemary until fragrant, about 1 minute.
Remove from heat. Stir in bread and sausage; season with salt and pepper, to taste. Stir in chicken stock until absorbed and well combined. Let stand 5 minutes, stirring occasionally, until liquid is absorbed.*
Spread bread mixture into the prepared baking dish. Place into oven and bake until top is browned, about 30-35 minutes.
Serve immediately.
Notes
*This can be made 1 day ahead. Let cool; cover and chill.