Spread potato pieces onto a baking sheet and drizzle with olive oil.
Roast in the preheated oven until tender, about 45 minutes; remove from oven and let cool at least 15 minutes.
Place roasted potatoes into a large salad bowl and combine with hard-cooked eggs, celery, green onion, and bacon; stir in mayonnaise and season to taste with salt and black pepper. Cover and refrigerate for 1 hour to let flavors blend.