Heat the oven to 190C (170C)/gas 5. Put the shallots, garlic cloves, grapes and root vegetables into a large baking tray, then add two tablespoons of olive oil and some salt and pepper. Roast for 25 minutes, until the root veg is starting to soften.
Remove the tray from the oven and add the sourdough, sage, parsley stalks and capers, and toss. Add two more tablespoons of oil and bake for a further 10 minutes, until everything is tender and golden, adding the greens for the last five minutes.
In a jar or small bowl, shake or whisk together the dressing ingredients, then pour over the tray, scatter with the parsley leaves, toss and serve.