Preheat the oven to 220 degrees Celsius/ 430 degrees Fahrenheit.
Wash leeks: Wash the leeks. Trim and discard the roots and the last 2 cm/ 1 inch or so of the dark green ends as well. Slice the leeks lengthwise. Carefully fan open the layers without taking the leek apart and rinse under running water until all the dirt is removed.
Cut leeks: Cut the halved leeks into smaller pieces, about 10 cm/ 4 inches long. Place the leek pieces in a roasting tin.
Season: Whisk together the oil and the spices. Pour over the leeks and massage well with your hands to make sure that all the leeks are coated in oil.
Roast the leeks for about 40 minutes. Start checking after 25-30 minutes, about every 5 minutes or so; the roasting time depends on the thickness of the leek halves and your oven. When done, the roasted leeks should be tender easy to pierce with a fork.
Remove the outer leaf before serving. Sprinkle with chopped parsley and serve as suggested above.
Notes
Both paprika sorts are optional, you can only use salt and pepper or other spices instead.