Preheat the oven to 425 degrees.
Cut the cauliflower crosswise (from top to bottom) into 1/2-3/4-inch thick slices, removing and discarding the leaves and stem. Cut the potatoes into 1/2-inch thick wedges.
Lay the vegetables on a very well oiled baking sheet in a single layer, arranging so that the flat, cut sides are touching the pan.
Spritz or brush with a light coating of olive oil. You need just enough to make the seasoning stick. Then, sprinkle with the rosemary, salt and pepper and roast for 20 minutes or until the bottoms are golden brown. Using a spatula, I like to peek underneath the vegetables after 15 minutes or so to make sure they are not browning too quickly. (All ovens vary somewhat. If the veggies are sufficiently browned but still too firm for your taste, toss and continue baking, checking in 5-minute increments. )
When just cooked, remove vegetables from the oven, and switch to the broil setting. Sprinkle with the blue cheese and broil, watching very closely, for 1-2 minutes or until the cheese is melted and the tops of the veggies are golden brown.
