Preheat oven to 400°F. Place a large rimmed baking sheet on the upper rack to preheat.
Spread the rinsed chickpeas on a clean kitchen towel or paper towels; gently rub to dry them and loosen the skins. Discard any loose skins.
Transfer the chickpeas to a large bowl. Add 2½ tablespoons pickle brine, 1 tablespoon vinegar, 1 tablespoon oil and ½ teaspoon salt; toss to coat.
Carefully spread the chickpeas in an even layer on the hot baking sheet. Roast, stirring once halfway through, until crispy and golden, 35 to 40 minutes.
Combine 1½ teaspoons dried dill, ¾ teaspoon garlic powder and ¾ teaspoon onion powder in a small bowl. Sprinkle the seasoning over the hot chickpeas and toss to coat.
Let cool completely, about 10 minutes. Garnish with fresh dill before serving, if desired.
