vegetarian chillie/curry, vegetarian lasagne. you could make a mash with the cauli and broc, add grated cheese and bake it. stir fry some of it with a nice sauce or seasoning. leeks in cheese sauce. don't people use courgettes to make cakes and bread? the list goes on...
I would cut it up into small pieces, place in a roasting tin and drizzle some olive oil with a bit of honey and mustard mixed in and then roast the veg. When it is done, roll out some puff pastry and cut into squares, pile the veg on the pastry, sprinkle some grated cheese over and bake.