Stir the celery with the red bell pepper, parsley, 1/4 cup (50 ml) mayonnaise, the green onion, mustard, garlic, salt and pepper. Stir in the crab and 1/2 cup (125 ml) breadcrumbs just until well combined. Form the mixture into 12 balls. Place the remaining breadcrumbs in a shallow dish. Roll each ball in the breadcrumbs until evenly coated; place on a parchment paper-lined baking tray. Freeze for 1 hour.
Meanwhile, place the remaining mayonnaise, roasted red peppers, sour cream and lemon juice in a food processor. Pulse until mixture is smooth. Season with salt and pepper to taste; set aside.
Turn the grill on. Select the Manual mode program, select red color setting and press OK. Lightly grease the cooking plates with cooking spray. Once the purple indicator light has stopped flashing, place the crab cakes on the grill and close the lid.
Cook, in batches, for 3 minutes or until heated through and well marked. Serve the crab cakes with the roasted red pepper sauce on the side.