Preheat the oven to 200°C (400°F) and take out a baking sheet with high sides. You can line the tray if preferred.
Prepare the vegetables. Cut the cauliflower into florets, then cut the cauliflower stem, pumpkin, and potatoes into pieces about 2cm (¾ in.) in size. Add to the baking tray.
½ medium head cauliflower, ½ medium pumpkin, 2-3 medium potatoes
Add the chickpeas. Top with the oil, salt, pepper, and cumin, and use your hands to mix well to coat the vegetables.
250 grams (14 oz.) cooked or canned* chickpeas, 2 teaspoons oil, 1 teaspoon sea salt, ½ teaspoon black pepper, ½ teaspoon cumin
Bake for 30-40 minutes, opening the oven once or twice to vent the steam. If you cook for the full 40 minutes, stir the tray bake after the first 30 minutes so that it doesn't burn. The extra ten minutes will make the vegetables more crisp and brown, but you have to watch that the cauliflower florets don't burn.
Serve hot, optionally topped with tahini garlic sauce and parsley. Leftovers are good cold and can be kept for a couple of days in a sealed container in the refrigerator.
Notes
* A 400 gram (14 oz) can of chickpeas is usually about 240 grams of chickpeas when drained and rinsed.