Preheat the oven to 400°F. Wrap the garlic in tin foil, drizzle with olive oil, and roast until very tender and fragrant, about 20 minutes.
Remove the roasted garlic cloves from the head and place in a blender, along with the remaining dressing ingredients except the oil. Purée until smooth, adding water if necessary. With the motor running, drizzle in the oil until emulsified. Season to taste.
Toss the salad ingredients in a large bowl. Mix with creamy lemon dressing and serve.