Preheat the oven's broiler, and set the oven rack at about 6 inches from the heat source. Line a baking sheet with aluminum foil. Place the peppers, cut sides down, onto the prepared baking sheet.
Cook under the preheated broiler until the skin of the peppers has blackened and blistered, about 5 minutes. Place the blackened peppers into a bowl, and tightly seal with plastic wrap. Allow the peppers to steam as they cool, about 20 minutes. Once cool, remove the skins and dice. Set aside.
Heat the olive oil in a large saucepan over medium heat. Stir in the celery, garlic, and onion; cook and stir until the onion has softened and turned translucent, about 5 minutes. Stir in the roasted red bell pepper and crabmeat, and season with rosemary and lemon pepper. Pour in the chicken stock, and simmer for 10 minutes. Slowly stir in the dry potato flakes, and cook until thickened.
Pour the soup into a blender, filling the pitcher no more than halfway full. Hold down the lid of the blender with a folded kitchen towel, and carefully start the blender, using a few quick pulses to get the soup moving before leaving it on to puree. Puree in batches until smooth and pour into a clean pot. Alternately, you can use a stick blender and puree the soup right in the cooking pot.
Return the pureed soup to the saucepan. Stir in the milk and sour cream, and cook over medium-low heat until heated through, about 5 minutes. Top with Asiago cheese before serving.