2 lb (800 gr approximately) pork roast
2 tablespoons fresh herbs (thyme, marjoram), finely chopped
1/2 lb (200 gr) prosciutto, finely sliced
2 tablespoons extra-virgin olive oil
1 tablespoon butter
2 oranges, juiced
1 carrot, chopped
1 stick celery, chopped
1 small onion, chopped
1 orange, sliced