Cauliflower: Put an oven rack in the center of the oven. Preheat the oven to 400 degrees F. Spray a baking sheet liberally with vegetable oil cooking spray. Set aside.
In a medium bowl, toss the cauliflower and olive oil together until coated. Put in a single layer on the prepared baking sheet and season with salt and pepper, to taste. Roast until golden and tender, about 25 to 30 minutes. Set aside to cool for 10 minutes.
Salad: In a medium saucepan, bring the chicken broth, curry powder and salt to a boil over medium-high heat. Remove the pan from the heat and stir in the couscous. Cover the pot and allow the couscous to absorb the liquid, about 5 to 7 minutes. Fluff the couscous with a fork and transfer it to a large serving bowl. Stir in the cooked cauliflower, cranberries, cashews, cucumber, parsley, and lemon zest. Refrigerate until ready to serve.
Dressing: In a small bowl, whisk together the yogurt, olive oil and curry powder until smooth. Whisk in the lemon juice and season with salt and pepper, to taste.
Just before serving, add the dressing to the salad and toss well to coat.