Preheat the oven to 375 degrees F (190 degrees C). Line a rimmed baking sheet with parchment paper.

Halve squash lengthwise; discard seeds and membrane. Place squash, cut sides down, on the prepared baking sheet. Roast in the preheated oven until tender, about 45 minutes. Scrape out pulp; set aside.

Melt butter in a large pot over medium heat. Stir in onion, garlic, curry powder, ginger, and salt. Stir until onion is soft, about 10 minutes. Add broth; bring to a boil. Stir in pears and reserved squash; simmer until pears soften, about 30 minutes.

Purée in batches in a blender until smooth. Return soup to the pot; stir in half-and-half. Reheat on low until warmed through.