What Breed is My Dog?

I am getting a couple of puppies from one of my friends and we are trying to figure out who the father is to them. The mother is a chocolate Lab/German Shepherd mix, but we don't know the father. There are a couple different male dogs on her street, but we think it's probably the Rottweiler because of some of the puppies' coloring.

Right now they are 4 weeks old so it might be hard to tell, but any help will be appreciated.

By Hannah F.