Step 1Cook the couscous according to the instructions on the package. Rinse in cold water, drain well, put in a bowl and set aside. Heat the oven to 450 degrees.
Step 2In a separate bowl, toss the cauliflower with the curry powder, turmeric, cumin, coriander, salt, cayenne, brown sugar and oil. Spread out on a foil-lined rimmed baking sheet and roast in the oven until cauliflower is browned around the edges but still crunchy, about 10 minutes. Remove just the cauliflower and put it in the bowl with the pasta.
Step 3On the same rimmed baking sheet, place the carrots and, using a spatula, toss the carrots with the leftover spices and oil. Roast the carrots until brown around the edges but still crunchy, about 8 minutes. (If you find that the spices and oil are a little overly browned from roasting the cauliflower, toss the carrots using the same proportion of new spices, salt, sugar and oil.) Add to the couscous.
Step 4Fold in the vegan mayonnaise, cilantro and lime juice with the pasta. Taste, and adjust spices and seasoning if desired. Refrigerate, covered, until ready to serve.