Preheat oven to 400° F.

Place two rimmed baking sheets in the oven for 4 minutes to heat. Meanwhile, toss carrots, pears, 1 1/2 tablespoons oil, salt and pepper in a large bowl. Carefully spread vegetables on hot baking sheets. Roast until tender and golden, 20 to 25 minutes, shaking the pan once or twice to turn vegetables.

Meanwhile, heat remaining olive oil in a heavy stockpot or Dutch oven over medium heat. Add onion and cook until soft and translucent, about 8 minutes. Stir in garlic, 1 1/2 teaspoons ginger and curry powder, cooking for 1 additional minute. Add roasted carrots and pears and pour in enough vegetable stock to cover; bring to a boil. Lower heat to a simmer and cook, partially covered, for 20 minutes.

Let cool slightly. Carefully puree soup until smooth (either with an immersion blender or in batches in a blender or food processor). Return soup to the stove to reheat, adding milk to taste and desired consistency.

In a small bowl, combine crème fraîche with remaining ginger and a pinch of salt. Ladle soup into bowls, add a dollop of crème fraîche and sprinkle with pistachios.