Preheat the oven to gas 6, 200ºC, fan 180ºC. Boil the kettle, then pour the water into a saucepan set over a high heat. Add the whole shallots and simmer for 2 minutes. Drain and refresh under cool water, then slice the bases off and peel. Cut any large shallots in half.
Combine all the ingredients in a large roasting tin and mix. Roast for 50-55 minutes, until the veg is soft and caramelised. This side dish is perfect with roast turkey, but suits any roast. It can be cooked a day ahead, then reheated until piping hot.