Preheat oven to 400 F.
Cook cous cous according to package directions, adding 1 tsp salt to cooking water. Arrange asparagus on lined baking tray, sprinkle with oil, toss, sprinkle generously with salt and pepper. Roast until crisp-tender about 12 to 15 min.
Whisk together the dressing in a bowl.
When cous cous is cooked, transfer to large mixing bowl with asparagus and dressing, with roasted peppers, olives and cannellini. Mix well.
Just prior to serving, drizzle with a bit of olive oil, and the juice of another 1/2 lemon. Top with lemon zest.