Heat oven to 400° F. On a rimmed baking sheet, toss the squash with 2 tablespoons of the oil, ½ teaspoon salt, and ¼ teaspoon pepper.
Roast the squash, tossing once, until tender, 20 to 25 minutes.
Place the squash, lettuce, pepitas, and ¼ teaspoon each salt and pepper in a large salad bowl. Drizzle with the vinegar and the remaining oil.
Toss the salad gently. Serve with warm bread.