Bring a large pot of salted water to a boil. Add the pasta and cook as the label directs. Reserve 1 1/2 cups cooking water, then drain the pasta. Meanwhile, put the carrots, walnuts, garlic, oregano, lemon zest, 1/4 teaspoon salt and the red pepper flakes in a food processor and pulse until finely chopped. Heat the olive oil in a large nonstick skillet over medium-high heat. Add the walnut-carrot mixture and the raisins and cook, stirring frequently, until the carrots soften and begin to brown, about 5 minutes. Add the reserved cooking water and bring to a simmer, then add the pasta, pecorino, lemon juice, parsley, and salt to taste and toss. Divide among bowls and top with more cheese.