Preheat the oven to 450 degrees F. Line a baking sheet with parchment paper. Set aside.
In a bowl, toss together potatoes, olive oil, salt, and pepper until evenly coated. Transfer the potatoes to baking sheet. Roast in the oven for 20-25 minutes or until browned.
In the meantime, add cilantro, garlic, vinegar, lime juice, oregano, red pepper flakes, olive oil, salt and pepper to a food processor. Pulse about 4-5 times then transfer to a bowl. You want the mixture to look thick and roughly chopped, not like a green sauce. Taste and adjust seasonings, if needed. What you want is a strong cilantro garlicky taste.
Remove the potatoes from the oven, toss with chimichurri, and serve hot. Enjoy!