Preheat the oven to 200C.
Peel the carrots and potatoes, then chop into chunks.
Peel the onions and slice both into 8 segments.
Thinly slice the garlic and ginger .
Place all the chopped and sliced vegetables into a baking tray. Add the oil, lemon zest and lemon juice. Season and toss well. Roast in the oven until the vegetables are just tender (about 30-40 minutes).
Heat the stock in a large saucepan, add the roasted vegetables and juices. Bring to boil, then turn off the heat.
Add the thyme leaves and parsley then, using a liquidizer or hand-held blender, process until smooth and creamy.
Serve warm with crusty bread.