Scrape the seeds from the pumpkin halves and discard.
Brush the insides of each pumpkin half with the tablespoon of oil, ½ teaspoon salt, and ¼ teaspoon pepper.
Place the pumpkin halves face down on a baking sheet and bake for 45 minutes.
When the pumpkin has 20 minutes left of cooking time, add the remaining oil to a pot and bring the heat to medium-high.
Sauté the leeks and garlic for 5 minutes.
Add the coriander, cumin, ginger, turmeric, dry mustard, cinnamon, broth, lentils, and 2 cups water. Bring to a boil, then lower to medium-low and cook for 20 minutes covered, or until the lentils are tender.
Remove the cooked flesh from the pumpkins and discard the shell.
Add the cooked pumpkin to the pot and stir.
Blend the soup in a blender working in batches.
The curried roasted pumpkin soup is ready to serve. Top the soup with pumpkin seeds and parsley, if desired.