Preheat the oven to 350°F (180°C) and line a large sheet pan with parchment paper.

Place the pumpkin on the sheet pan and add 2 tablespoons of the olive oil, the honey, nutmeg, salt, and pepper. Toss until the pumpkin is evenly coated, then spread it in a single layer. Roast for 35 to 40 minutes, tossing halfway, until the pumpkin is tender and caramelized at the edges.

While the pumpkin roasts, heat the remaining 1 tablespoon of olive oil in a large stock pot over medium-low heat. Add the onion, garlic, and celery and cook for 8 to 10 minutes, stirring occasionally, until the onion is soft and golden. Lower the heat if the onion starts to brown too quickly.

Add the roasted pumpkin (and any honey from the pan), the stock, and the rosemary to the pot. Bring to a simmer, then purée with an immersion blender until completely smooth. Alternatively, carefully blend in batches in a countertop blender, filling it no more than halfway and venting the lid, then return the soup to the pot.

Return the pot to medium-low heat and stir in the cream. Simmer gently for 2 to 3 minutes, then taste and adjust the seasoning. Thin with a little extra stock if the soup is too thick.

Ladle into bowls and serve with crusty bread.