Preheat oven to 400 degrees F. Line a large baking sheet with parchment paper; set aside.
Add potatoes to a large bowl followed by olive oil and pesto; toss until evenly coated. Add ranch seasoning, onion powder, and pepper; toss well. Arrange potatoes in a single layer on the baking sheet.
Bake for 45-60 minutes or until tender and golden in some places, stirring half way through.