Heat oven to 200C / 180C fan / gas 6. Cut the peppers and squash into bite-size pieces (leave skin on the squash) Tip all the veg into a baking tray, add garlic, 2tbsp oil and seasoning, then mix and roast for 20minutes. Add the onion, cumin, harissa paste and almonds. Roast for another 20minutes, then cool.
Put couscous into a large bowl, pour over the stock, cover, and set aside for 10 minutes. Fluff up with a fork.
In a bowl, mix zest, juice, and remaining oil. Squeeze garlic pulp from skins into the bowl, mash well and fold in the mint. Pour over the veg, then toss with the couscous.