Bring a large pot of salted water to a boil. Add the pasta. In a large skillet, heat the oil and add the garlic. When golden, add the arugula. Mix well. When beginning to wilt, add 1/2 cup of the pasta cooking water.
Cook the pasta until al dente. Drain the pasta, retain 1 cup of the cooking water. Add the pasta to the arugula, and cook together over medium heat until well mixed. Add some of the retained water if it seems dry. Serve immediately with a generous sprinkle of Pecorino Romano.
