Elana - You can cook the chicken either at a high temp or a moderate one. I prefer the more moderate one because the high temp tends to get the oven too dirty. I can't help you with a potato, because I don't cook them. Most vegetables should be done within the hour that it takes a chicken to cook at 350-deg. F. but as I said, I don't know about potatoes. It also helps to put the tail end of the chicken into the oven first, since the back of the oven is the hottest part of most ovens.

I find it easier to cut the chicken into halves, but you wanted a whole one, so here's what Barbara Kafka has to say in her "Roasting"

"Nothing is simpler. Put the rack in the second position from the bottom of the oven, crand the temperature up to 500-deg. F. and go.
The basic roasting time for chickens in the high-heat method is about 10 minutes to the pound for a chicken at room temperature, untrussed, which invariably gives a crisp skin and a thoroughly cooked but moist bird. However, it may be necessary to cook free-range chickens with their heavier thighs and legs and greater amount of blood for a longer time. Chickens need to be thoroughly cooked, but not until powdery dry. Interior juices should be clear, and the tip of a knife inserted into the joint between the thigh and carcass should reveal no blood.
"Co-dependent vegetables: Roasting potatoes along with a chicken may be the most common example. Any of the birds can be roasted with potatoe wedges (a large floury baking potato makes about twelve wedges) added to the pan. Don't cram the pan. If more vegetables are desired, use a large pan to accommodate them along with the bird for the last 40-50 minuts of the roasting time. If the potatoes are added to the pan when the bird begins roasting or slightly before, they will need to be filmed with a tablespoon of fat. If the bird has roasted for a hwile before the potatoes are added and has rendered some fat, the potatoes are simply rolled in the fat that has been rendered from the bird. The more fat, the more the potatoes will brown. Scoop up the ptoatoes once or twice to turn them and keep them from sticking to the pan."

The problem with her recipe is that it calls for a 5- to 6-pound chicken and I don't see those in my grocery store. I did use her recipe once and roasted my 3 pound chicken at 500 for 30 minutes and it wasn't done, so I finished it in the microwave oven and it was delicious.

I cut mine in 1/2 and microwave them for 20 minutes and then roast the two halves at 350-deg. F. for about 45 minutes and they usually come out great. I use my convection oven for this and the skin is crisp, the way we like it. But I don't do vegetables with them. I always cook those on the stove top. Hope that this is of some help to you.