Heat the oil in a saute pan over medium heat.
Next, add the onion and serrano pepper and stir for 5 minutes, or until the onions have softened.
Add the sausage and garlic and cook until the meat is no longer pink.
Add the potatoes, 1 tablespoon of the rosemary and any remaining spices. Cook for 10 minutes or until the potatoes become fork tender.
Add the remaining 1 tablespoon of rosemary, mix well and serve.