When it's good, it's very, very good...
If you're passionate about cauliflower, you'll find that tossing it in oil then roasting it intensifies and transforms the taste, giving a deep, nutty, flavour. You could eat it on it's own like this, with a sprinkling of sea salt, or use it in other dishes, such as this cauliflower cheese dish. I think it's perfect for cauliflower cheese, because it means you avoid two heinous crimes against said dish, being either a watery sauce leaching out from soggy cauliflower (from the juices leaking out) or a stodgy lump you can pick up on your fork, from the dish cooking too long and all liquids evaporating. Yes, you know what I'm talking about! (Don't mention this to Grandma).

I have given you two versions, naughty and nice - one for the sinful amongst you, made with a traditional Béchamel and plenty of cheese, the other equally tasty, but with a lighter gluten-free version of a Béchamel sauce, both topped with a Parmesan cheese crumb. How much, if any, of the Parmesan crumb you choose to sprinkle on is up to you - you may just decide you prefer to have grated cheese on top. Or nothing extra. What you will get, though, is delicious cauliflower in a silky sauce. If you want to make it a little more punchy, add a spoonful of Dijon or English mustard to the sauce, and if you haven't got time to infuse the milk with the onion, you could cheat and add a little onion powder / granules instead.