Grind 2 cups of the oats in a food processor into a fine powder. Add the Nutella and salt and process until a smooth mixture forms. Add the remaining ⅔ cup of oats and pulse to combine.
Roll level tablespoons of the dough into balls. Roll in the cocoa to coat. Repeat to coat evenly. Refrigerate for at least 1 hour and up to 5 days.
Storage suggestion: Keep the cookies refrigerated for about 5 days.