Preheat the oven to 400°. In a medium baking dish, combine the carrots with the olives, water, garlic, oil and butter and season with salt and pepper. Cover with foil and roast for 30 minutes, until tender. Uncover and roast for about 30 minutes longer, until the water has evaporated and the carrots are lightly browned in spots. Transfer the carrots, olives and garlic to a plate and serve.