Remove casings from sausages and cut into 1-inch pieces. Place these into a 10x15-inch roasting pan. Layer the potatoes, carrots and onions over the sausages. Then pour the tomatoes over all. Season with salt, ground black pepper and oregano.
Cover and bake at 375 degrees F (190 degrees C) for 60 minutes, then uncover and bake for 15 to 20 more minutes.