Preheat the oven to 450 degrees. In a large bowl, toss the cauliflower with 2 Tbsp olive oil and a pinch of kosher salt. Spread into a single layer on a parchment-lined baking sheet and roast for about 25-30 minutes, tossing once halfway through, until cauliflower is tender and starting to brown. Meanwhile, whisk together the mayonnaise, remaining 1 Tbsp Korea sauce, vinegar and lemon juice. Season to taste with salt and set aside. Remove cauliflower from the oven and return to a large mixing bowl. Add in ⅓ cup Korea sauce and the white part of the scallions. Toss gently to coat. Spoon cauliflower onto Bibb lettuce cups. Top with shredded carrots, peanuts and sliced scallion greens. Drizzle with Korea-spiced mayonnaise and serve warm.