In a container or zip-top bag, combine the shrimp and marinade ingredients. Marinate for 4-12 hours.
Preheat the oven to 350°F.
In a small saucepan, combine the couscous, olive oil, 2 cups of water and ½ teaspoon salt. Bring to a simmer, turn off the heat, cover and let sit for 15 minutes, until the grains are tender. Fluff the couscous with a fork.
Toss the shallots with the canola oil on a baking sheet and roast for 20 minutes. Cool slightly, then place in a blender along with the vinegar, salt, sugar, egg yolk, garlic and mint. Purée until smooth. With the motor running, drizzle in the oil until emulsified. Season to taste.
On a baking sheet, toss the cauliflower with the oil and a pinch of salt and pepper. Roast until beginning to brown, 12-15 minutes.
Toss the shrimp on a baking sheet and roast for 5-7 minutes, until cooked through and pink in color.
In a large bowl, toss together the romaine, arugula, roasted cauliflower, pumpkin seeds, and shallot vinaigrette. Divide between bowls and top with couscous and shrimp.