Preheat the oven to 425°F (220°C). Line a large baking sheet with parchment paper and set aside.
Cut the potatoes in half (leave the skins on). If any potatoes are much larger than the others, cut those into similar-sized pieces so all pieces cook evenly.
Put the cut potatoes in a large bowl. Add 2 tablespoons olive oil, Kosher salt, and freshly ground black pepper to taste.
Toss the potatoes in the bowl until they are evenly coated with oil and seasoning.
Transfer the potatoes to the prepared baking sheet and spread them into a single even layer with a little space between pieces (do not overcrowd).
Roast the potatoes in the preheated oven for 20 minutes, then use a spatula to flip each piece so the other side can brown.
Roast an additional 15 to 20 minutes, until the potatoes are tender all the way through and crisp on the outside.
Remove the pan from the oven and transfer the potatoes to a large serving bowl. Add chimichurri sauce to taste and toss until the potatoes are well coated.
Garnish with queso fresco, if using, and serve immediately.