Pedigree is a very poor quality food.
Take a look at the ingredients list on the back of the bag...it's corn, corn, and more corn and by-product meal. This food has very little meat in it.
I would suggest you do some reading on the Nutrition Forum and see what foods are most often recommended here...they will most often be a food that uses human grade meats, and no corn, wheat or soy products...and no by-product meal.
As far as the undercoat...an improved diet may help with that...or it could just be the way your Rottweiler is bred and genetics? Did your dog come from a BYB or a shelter? Most often dogs that are not well bred have undercoat showing.
Gina