Preheat the oven to 350 degrees F. Spread the softened butter in a medium baking dish or gratin dish.
Toss the cubed bread with 2 tablespoons olive oil and the Italian seasoning in a large bowl. Transfer to a baking sheet and bake until crispy, about 10 minutes.
Heat a large pan over medium-high heat. Add the remaining 2 tablespoons olive oil and the sausage. Cook the sausage, stirring and breaking up the meat, until brown, 8 to 10 minutes. Turn the heat to medium and add the onion, carrots and celery and cook until the vegetables are tender, 6 to 8 minutes. Add the garlic and cook for 1 minute, then add the rosemary and sage and cook for 1 more minute. Season with salt and pepper.
Combine the toasted bread, sausage, vegetable mixture and raisins in a large bowl. Combine the stock and egg in a medium bowl and whisk until well blended. Add the stock mixture to the bread mixture and fold together.
Transfer the stuffing to the prepared baking dish and bake until the top is crispy and hot through the center, 35 to 45 minutes.