Roasting a duck takes around 1 hour and 30 minutes to 2 hours depending on the size of the duck.
Make sure to thaw the duck out overnight in the refrigerator before you get ready to roast the duck as it will take less time roasting a thawed duck than roasting a frozen duck.
Preheat your oven to 425 F and allow the duck to roast and brown lightly for 15 minutes and then reduce the oven temperature to 350 F degrees and then allow it to roast in the oven for another 1 hour and 25 to 1 hour and 30 minutes.
If you have a meat thermometer then you can tell when the duck is fully cooked when the internal temperature of the duck is 165 F.
So continue to roast the duck until the internal temperature is 165 F.
The duck should be fully cooked and roasted within 1 hour and 30 minutes but you can continue to roast it a little longer depending on how well done you want the roasted duck to be cooked.
It should take around the same amount of time to roast the duck in an electric roaster but it might take an additional 30 minutes to fully cook depending on the size of the duck.