One of the problems with roasting duck breasts and duck is the amount of fat that comes off it. This is a good thing in one way, but can spoil the roasting process.
You can of course roast the duck breasts on a rack of some kind, so that the fat collects in the bottom of the pan but the duck is kept above it.
The process I use combines pan frying and roasting.
I score the skin of the duck breast and heat a frying pan on a high heat.
Do not add any oil to the pan and place the duck breasts in the pan skin side down.
Once the skin is crisp, transfer the duck breasts to a heated roasting tray and place in the oven and cook until the duck is cooked to your liking.
Some prefer their duck rare, I personally like it a little more done myself.