Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
In a large mixing bowl, toss the halved baby potatoes with 3 tablespoons of olive oil, 1 1/2 teaspoons of salt, and 1/2 teaspoon of pepper. Ensure each piece is evenly coated.
Arrange the potatoes cut side down on the prepared baking sheet, spreading them out to prevent overcrowding.
Roast in the preheated oven for 30 minutes, flipping halfway through. The potatoes should be golden and crisp around the edges.
While the potatoes roast, whisk together the remaining 2 tablespoons of olive oil, red wine vinegar, minced garlic, and the last 1/2 teaspoon each of salt and pepper in a small bowl.
Once roasted, transfer the crispy potatoes to a large serving bowl. Drizzle the garlic vinaigrette over the top and toss until the potatoes are fully coated.
Sprinkle with green onions and parsley for a fresh, herby finish.