Step #2 Chop the peeled & deseeded butternut squash, sweet peppers, sweet potato, onion & carrot into nice big chunky pieces - 2inch diameter will be fine.
Step #3 Cut the tomatoes into similar sized chunks, & remove the seedy-jelly bit.
Step #4 Toss the vegetables with the olive oil until they're nicely coated & add the rosemary.
Step #5 Place in the oven for about 1 1/2 - 2 hrs, adding the whole garlic bulb after the first hr.
Step #6 The veg should now be cooked, slightly caramelised & almost chewy, with a much more intense & mellow flavour.
Step #7 Remove the rosemary sprigs & place all veggies in a pan.
Step #8 Squeeze the garlic out of their papery husks into the pan too & add stock.
Step #9 If there is any gooey residue on the bottom of the roasting tin, pour a little of the stock into it & scrape it into the pan, as this is where the serious flavour is!
Liquidize the soup in batches & reheat.
Step #10 Check seasoning & serve in big bowls with a swirl of greek yogurt on top.