Peel & cut into 3cm cubes the sweet potatoes and squash
Chop the onions into large wedges (about 6 per onion)
Separate the garlic cloves from their head, but don't peel!
Preheat the oven to 200C/Gas Mark 5
Mix the vegetables with the oil & harissa & fresh rosemary in a large roasting tin.
Put in the oven to roast for around 25 mins. Turning once or twice so all the vegetables are soft on the inside & caramelised on the outside.
If you have loads of other dishes going in & out of the oven, this can happily sit at the bottom of it keeping warm without much trouble. Cover it over with some foil if you think it might dry out.
Season to taste & serve with a few extra fresh sprigs of rosemary and a good sprinkle of pomegranate seeds.