Preheat oven to 200˚C, fan on.
Slice the fennel bulbs into chunky thick slices. Arrange the slices on a large baking tray in a single layer. Drizzle a little olive oil over the fennel and season well with salt and pepper.
Roast for about 25 minutes until the fennel is very tender and golden.
Remove the fennel from the baking tray and keep at room temperature. (If your oven is large enough you can roast all veg simultaneously)
Using scissors, slice grapes into small bunches. Add the grapes to the baking tray and season with a little salt and pepper. Bake for 10 minutes until just blistering.
Toss mushrooms in a bowl with the olive oil, garlic, red wine vinegar and Dijon mustard. Season lightly and mix well.
Add the mushrooms to the roasting tray of grapes and continue to roast together until the mushrooms are tender and the grapes are soft and juicy. About 7 minutes.
Allow mushrooms and grapes to cool slightly to avoid making the lettuce wilt.