Preheat oven to 425° F. Toss cauliflower with 1 tablespoon olive oil, and season with salt and pepper. Spread on a medium baking sheet and roast for 30 minutes, tossing halfway through, until very tender and well browned in spots.
Meanwhile, make the sauce by combining all the romesco ingredients in a blender and blending until smooth.
Heat a large skillet over medium heat. Add the pine nuts and cook until golden brown and toasted, about 5 minutes. Remove nuts from the pan and set aside.
In the large skillet over medium heat, add 2 tablespoons olive oil. Once oil is hot, add sliced leeks. Cook, stirring occasionally, until golden brown, about 10 minutes. Remove from the oil and place on a paper towel lined plate. Sprinkle with salt, and set aside.
Cook the pasta until al dente according to package instructions in a large pot of salted water. Before draining, reserve one cup of pasta water.
Add the pasta back to the pot. Add about 2 cups of the romesco, one half cup of pasta water, roasted cauliflower, and pecorino. Stir until combined, and adjust salt to taste.
Serve the pasta topped with crispy leeks and pine nuts. Top with additional grated pecorino and chopped parsley.