1Position 1 rack in top third and 1 rack in bottom third of oven and preheat to 375°. Spray 2 large rimmed baking sheets with nonstick spray. Toss potatoes with 1/2 cup olive oil in large bowl. Sprinkle generously with salt and freshly ground black pepper. Spread potatoes in single layer on baking sheets, dividing equally. Roast 30 minutes.
2Meanwhile, whisk extra-virgin olive oil, lemon juice, dill, and lemon peel in small bowl to blend for dressing. Toss garlic and 2 tablespoons dressing in another small bowl. Divide garlic mixture between baking sheets with potatoes and toss; reverse baking sheets and continue to roast until potatoes are tender and brown around edges, about 15 minutes longer.
3Toss roasted potatoes in large bowl with enough of remaining dressing to coat and serve.