first of all, you have to choose the right duck to roast. if you buy from the local market chances are they are so fat that after all the grease melt away, you won't have much meat to eat.
But still, you could try with local duck for experience.
now how to roast it? i prefer the most simple way, that is with salt and pepper only so that i can taste the crispy skin and the soft and moistered meat, but you have to eat it right away after taken it out from the owem otherwise the meat will be harden by the change in temperature.
One very important principle to respect: don't let the duck cooked in its grease, it would give a bitter taste and the skin will not be crispy. So put it on a grill on top of an oven plate so that grease will fall in to the plate.