The nice thing about roasting potatoes is that you almost can't go overboard, as long as they don't get charred. The insides just get creamier and softer, while the outsides get crisper and more brown -- up to a point, of course. I often leave mine in for nearly an hour at 350, bassuming slightly larger chunks/wedges.

depends on the size of the potato chunks and the temperature of the oven. Let's say they are 1-inch chunks and the temp is 350. I'd check them and turn them with a spatula after 20 minutes, and keep them in the oven until nicely browned, probably 30 to 40 minutes total.