Preheat the oven to 400˚F and arrange a rack in the center of the oven.
Gather all ingredients. Prep the potatoes: They can be peeled or unpeeled, based on your preference. Cut them into roughly 1”-sized chunks. Hold the potatoes in cold water until cooking time to prevent browning.
3 pounds potatoes
Drain the potatoes if being held in cold water, then place them in a large bowl and toss with pesto until the potatoes are evenly-coated. Use additional pesto as needed.
¾ cup pesto,
Arrange the pesto-rubbed potatoes in a single-layer on a parchment-lined, rimmed sheet pan. Sprinkle them lightly with black pepper.
Freshly ground black pepper
Roast uncovered for about 20 minutes, or until the potatoes are tender when pierced with a knife. They should be both tender and crispy. Rotate the sheet pan once about halfway through the cooking process.
Remove the potatoes from the oven and turn the oven to broil mode. Sprinkle the potatoes evenly with the pecorino cheese, then return the sheet pan to the oven and broil for 2 to 3 minutes, watching it closely so as to prevent burning. Remove the potatoes from the oven immediately once the cheese begins to brown lightly. Serve immediately.
¼ cup grated pecorino cheese