I usually just roast my chickens on a sheet pan, but we're roasting a duck and I'm starting to fear that it won't be enough!!
I would use a turkey baster to remove the fat and juices as the duck roasts.
Do you have a 9x14 cake pan? I use that when I'm in a pinch. Alternatively, you could try a large cast iron skillet or a casserole dish. If your duck is too big for any of those, I would try splitting the duck in half and using two pans. Most ovens come with a broiler pan in which case I would use that as a last resort. Or there's always the dollar store for those throw away aluminum ones.
I would just use one of the cheap disposable aluminum ones from the dollar store and put it on the sheet pan to improve handling.