Peel a red onion and chop it into eighths. Peel some pumpkin and cut it into similar-sized chunks, about the same amount of pumpkin as there is red onion or maybe a little more. Put them in an ovenproof dish, drizzle generously with olive oil, turn to coat and roast until soft (30-60 mins depending on temperature and your oven's performance).
When it's done, or 10-15 mins before if you're in a rush, put the kettle on to boil and make some vegetable stock from a stock cube (following packet instructions) and heat some olive oil in a pan. When it's hot add risotto rice and turn to coat. After 1-2 mins add some of the stock and leave the rice to absorb it. When it's been taken up, add more liquid a ladleful at a time until it's done (unfortunately I do this by eye so can't guide you very well - if you've not made risotto before, you can either taste it to check the rice is fully cooked or look up a risotto recipe (maybe on the rice packet?) to work out how much rice/liquid to use and you'll know it's done when all the liquid is taken up).
Stir in the pumpkin and red onion and leave for a couple of mins to heat through. Add zest from half a lemon and juice from half or quarter, depending on how juicy the lemon is. Stir it in. Add some chunks of blue cheese and when they are melted, stir again and serve! Enjoy