Preheat oven to 200 degrees C. Line a baking tray with baking paper.
Combine the pumpkin, olive oil, cumin, coriander, cinnamon, ginger, salt and pepper in a glass bowl. Gently toss until pumpkin is coated in spice mixture. Place as a single layer on the prepared baking tray. Roast in preheated oven, turning occasionally, for 30 minutes or until brown and tender.
Blanch the peas until bright green and heated through, then chill under cold running water. Drain.
Bring the vegetable stock to the boil over high heat. Add to a heatproof bowl with the couscous while stirring with a fork. Cover and set aside for 5 minutes or until all the liquid is absorbed. Use a fork to fluff up.
Transfer the couscous to a large serving bowl. Add the roast pumpkin, peas, chickpeas, lemon juice and coriander then gently toss until well combined. Taste and season with salt and pepper.
Stir the mint through the yoghurt and serve on top of the salad as a garnish.