Preheat oven to 375 degrees F. Line a 15x10x1-inch baking pan with foil. Add carrots to the prepared pan, drizzle with olive oil and toss to coat. Roast, uncovered, 20 minutes or until tender; set aside to cool.
In a large bowl stir together the yogurt, lemon juice, thyme, water, harissa paste, and salt. Add the carrots, chicken, celery, almonds, and raisins; stir to coat evenly.
Serve chicken salad mixture on toasted bread with lettuce.