Preheat the oven to 425 F (220 C)

Place the carrots and celery in a single layer on a large rimmed baking sheet. Drizzle with 2 tablespoons of olive oil and salt & pepper and toss to coat

Roast in the preheated oven for 25 minutes, turning once midway through cooking, until fairly tender and just starting to caramelize

In a stockpot or large dutch oven warm the remaining tablespoon of olive oil. Add the onion and saute over medium-high heat until it begins to soften and turn translucent, about 5 minutes

Add the garlic and ginger and saute until fragrant, about 1 minute more. Add the roasted carrots and celery and stir to coat

Pour in the vegetable stock, raise the heat, and bring to a boil

Add the half & half reduce the heat to low and simmer, partially covered, for 15 minutes, or until the vegetables are tender

Remove from the heat, and using a regular blender, carefully puree the soup

Season to taste with salt and freshly ground black pepper