Preheat the oven to 425°F. Line a 15x10-inch jelly-roll pan with aluminum foil or parchment paper.
Add to the bowl of a food processor (or jar of a blender): parsley, rosemary, garlic, lemon zest/juice, 2 tablespoons of oil and ½ teaspoon salt. Process until smooth, stopping to scrape down sides. Set aside.
In a large bowl, toss together the halved potatoes, ½ teaspoon pepper, remaining 2 tablespoons oil, and remaining ½ teaspoon salt; spread the potato mixture in a single layer on the prepared pan.
Bake for 25 minutes or until the potatoes are golden brown and tender, stirring after 10 minutes. Toss the potatoes with the lemon-and-herb mixture until evenly coated. Serve warm.