Bring a large pot of water to a boil and salt generously. Prepare an ice water bath.
To clean the broccoli rabe, remove the bottom third of the stem, which is fiberous. Remove the larger leaves, leaving the ones which are smaller at the top attached. Blanch the broccoli rabe in the boiling water for about 1 minute until bright green, then transfer to the ice bath to stop the cooking process. Remove the broccoli rabe to a baking sheet lined with paper towels and dry well.
Add the olive oil to a large cast-iron or stainless steel frying pan and heat over low heat. Add the chile flakes, anchovies and garlic and saute about 1 minute. Add the broccoli rabe and cook, tossing lightly in the oil to coat, until the broccoli rabe is heated through and tender, about 3 minutes. Season with salt and pepper. Top with the Pecorino Romano and serve.