There are two main reasons why roasted cauliflower turns soggy: overcrowding the pan, and using too much oil. The best way to avoid this is by using a large baking sheet where you can arrange the cauliflower in a single layer without crowding too much, and by watching the amount of oil you use in the recipe. I use about 1.5 tbsp of oil while first roasting the cauliflower and another 1 tbsp in the sauce to give it the right consistency!