Place the Creamer potatoes in a large saucepan and cover with cold water by 1 inch. Bring to a boil and cook until the potatoes are just tender (but not too soft) when pierced with a fork, 15 to 20 minutes. Drain.
In a medium bowl, toss the shrimp with 1 ½ teaspoons olive oil, ¼ teaspoon salt and ¼ teaspoon pepper.
Preheat the oven to 425 degrees F. Lightly coat a baking sheet with olive oil spray.
Arrange the potatoes on the prepared baking sheet. Partially smash each potato with the back of a fork. Brush the potatoes with 1 tablespoon olive oil. Sprinkle ¼ teaspoon and ¼ teaspoon pepper over the potatoes.
Roast the potatoes until they are starting to brown, 12 to 15 minutes.
Set aside 3 tablespoons of the chimichurri sauce for drizzling later. Spoon the rest of the chimichurri over the potatoes, then scatter the shrimp over the potatoes.
Return the potatoes and shrimp to the oven and cook until the shrimp are just cooked through, about 5 minutes. Take care not to overcook the shrimp.
Spoon the rest of the chimichurri sauce over the shrimp and potatoes. Serve.
The Chimichurri Sauce:
In a food processor, pulse the parsley, garlic, oregano, red wine vinegar and salt until the parsley is finely chopped, scraping down the sides as needed. Transfer to a bowl and stir in the olive oil.