Cut the potatoes to ¾ inch cubes. Place on a jelly-roll pan and toss with the oil, garlic powder, rosemary, paprika, salt and pepper. Roast the potatoes in the middle of a preheated 450°F. oven, turning them occasionally, for 15 minutes. Add the cauliflower, toss the mixture well, and roast 10 minutes or until the cauliflower is tender and golden in spots. Toss the vegetables with chives and serve topped with a garnish of whole chives.