Spread the vegetables out into two baking dishes, so there's a bit of room around them. Bake for 20-30 minutes, until pumpkin and fennel is soft and starting to caramelise.
Heat your stock in a saucepan, and leave to simmer.
heat a drizzle of olive oil and a knob of butter in a large pot and sauté the onion, garlic, and celery, until soft.
Add the arborio rice and stir for a minute or two, to lightly fry. Turn heat down to just above a simmer.
Add the wine, and stir until totally absorbed.
Add the stock to the rice, a ladelful at a time, until rice is tender. I find this takes 20-25 minutes. Stir constantly.
When rice is soft, check for seasoning. Add butter and cheese. Gently fold through the pumpkin and fennel and serve with extra cheese and the fennel fronds on top.