Preheat oven to 425°F. Line a baking sheet with parchment paper.
Wash the potatoes and cut them into ½” cubes, leaving the skins on. Toss them in the olive oil, salt, and pepper. Spread them evenly on a baking sheet, allowing enough room so they are not touching (use a second sheet if needed).
Bake for 25-30 minutes, tossing every 10 minutes, until all sides are golden brown and crisp. Remove from oven and allow to cool to room temperature.
When ready to serve, toss the potatoes with green onions, parsley, and vinaigrette, starting with ¼ cup and adding more to taste. Serve at room temperature.