In a large skillet, sauté the onion in the olive oil and butter over a medium heat. When translucent, add the rosemary, garlic, and pine nuts. Cook for a few additional minutes and then add the white wine. Cook for an additional 5-10 minutes. Add salt and pepper to taste.
Meanwhile bring a large pot of salted water to a boil and cook the pasta until al dente. Drain the pasta, retaining some of the cooking water. Add the pasta to the rosemary mixture and stir together until mixed well. Add some of the retained water if necessary. Sprinkle with pecorino cheese and serve immediately.