01 - Preheat oven to 425°F. Line a large baking sheet with parchment paper.
02 - In a large bowl, toss potatoes and onions with olive oil, kosher salt, black pepper, dried thyme or rosemary, and minced garlic if using until evenly coated.
03 - Spread the seasoned vegetables in a single layer on the prepared baking sheet, ensuring pieces are not crowded for even roasting.
04 - Roast for 35 to 40 minutes, flipping the vegetables halfway through, until potatoes are golden and tender and onions are caramelized.
05 - Remove from oven, garnish with fresh chopped parsley if desired, and serve warm.