Heat the oven to 170°C.
Cut the squash into wedges, the peppers into half. Arrange them on a baking tray. Scatter the garlic cloves around (in their skin). Mix the oil with the spices, then brush the veggies with this mixture.
Roast for about 30 minutes, until tender. Set aside to cool.
When cooled, remove and discard the skins of the garlic, squash and pepper pieces.
Put the flesh into a saucepan. Add most of the stock and, using a stick blender, process into a smooth, silky soup. Add more stock, if it’s too thick.
Add the fresh coriander leaves, then blitz for a few seconds.
Bring to a simmer, then serve immediately.