Preheat the oven to 425° and line two baking sheets with parchment paper.
In a large bowl, toss the cauliflower florets with half of the oil and ¼ teaspoon each of the sea salt, pepper, and garlic powder. Spread the florets out on one of the baking sheets. Toss the chickpeas together with the rest of the oil, salt, pepper, and garlic powder. Spread them out on the remaining baking sheet.
Bake for 35-40 minutes, or until the cauliflower is tender and has browned and the chickpeas are crisp. Allow to cool slightly.
While the cauliflower and chickpeas are roasting, mix together the dressing ingredients in a high-speed blender or food processer until smooth and creamy. If the mixture is too thick, add a little more water, a teaspoon at a time.
Place the lettuce in a large bowl and top with cauliflower, chickpeas, and pumpkin seeds. Drizzle on the dressing and toss everything together. Top with the chopped parsley. Serve chilled or at room temperature.