Preheat oven to 425°F. Coat a 13x9x2-inch baking pan with nonstick spray; add potatoes to pan. Drizzle with oil and sprinkle with salt and pepper; toss to coat.
Roast, uncovered, for 25 minutes, stirring once. Add sweet pepper and leek and and toss to combine. Roast about 10 minutes more or until potatoes are tender and brown on the edges and pepper pieces are just tender.