Preheat oven to 425°F.
In a large bowl, combine 2 Tbsp. of the oil, ½ tsp. salt, and 2 Tbsp. harissa; mix well.
Add cauliflower and toss to evenly coat.
Spread on a rimmed baking sheet and bake for 35 minutes, tossing once halfway through, until tender.
Remove from oven and toss with remaining 2 Tbsp. harissa; bake for another 5 minutes, until caramelized and charred in some spots
Meanwhile, prepare Tahini-Honey by combining remaining 2 Tbsp. olive oil, tahini, honey, lemon juice, remaining ¼ tsp. salt, and black pepper; stir with a whisk.
Whisk in 1 Tbsp. water to thin out to desired consistency.
Transfer roasted cauliflower to a bowl or serving platter.
Drizzle with tahini-honey.
Garnish with fresh parsley and sprinkle on a little lemon juice if desired
