Cut the tops off 6-8 carrots then wash and slice lengthwise. If the carrots are fatter than your finger, slice into quarters.
Cut 1 head of broccoli into florets, then cut the florets in halves or quarters. Peel the stems and cut into similar size pieces.
Wash 2 good handfuls of green beans, then trim the ends and cut in half.
Wash 1 sweet potato and peel off any abrasions. Slice into rounds, then cut the rounds into bite-sized pieces.
Toss each vegetable separately in a large bowl with 4 T. olive oil and 1/2 t. salt. Arrange each on one half of a baking sheet. You will need two sheets.
Using a very sharp knife, cut the ends off 2 unpeeled mandarin oranges and discard them. Slice the mandarins very thinly, saving any juice that is lost.
Distribute the mandarin slices in and around the vegetables. They should be touching the baking sheet.
Sprinkle 2 T. zatar seasoning evenly over all the vegetables.
Roast in the oven at 400 degrees. After 20 minutes, check each vegetable. The sweet potatoes will cook the quickest. Remove each vegetable (and the mandarins) from the oven when they are tender and browned, and place in a bowl.
Meanwhile, put 2 C. dry couscous in a large bowl. Heat water in a teapot. When it reaches a boil, pour over the couscous until just covered. Cover the bowl for 5 minutes, then fluff the couscous with a fork and cover for another 5 minutes.
Toss the couscous and vegetables together. Serve with Greek olives and feta cheese.