Here's how (adapted from Cooks Illustrated, Jan '07):
Preheat oven to 475 F. Line a rimmed baking sheet with foil. Cut the green stuff off a head of cauliflower leaving the stem intact (I cut off too much, so beware). Cut through the stem to section the cauliflower into eight wedges, arrange on the baking sheet. In a small bowl, mix a pinch of salt, a pinch of pepper and 2T oil. Drizzle this over the cauliflower sections. Rub the oil in with your fingers, then turn each wedge over and rub that side too. Cover the whole baking sheet snugly with more foil. Bake covered like this for 10 minutes. Then remove foil and bake 10 more minutes. Remove from oven, flip each wedge, bake for 10 more minutes and it's done! Allow to cool (5-10 mintues?), and enjoy.