rough or normal play

Question
My husband brought home a female golden retriever puppy and we already
have a 7-year-old female GSD.  They played fairly well the first day, but now
the GSD appears more rough particularly in the way she nudges the puppy
(who will fall on her back).  The GSD will engage the puppy in the nudging
until we stop her.  Is the GSD establishing dominance, herding the puppy or
simply being playful?  I'm not sure the younger one enjoys it because she it
seems like the GSD is pursuing (and obviously towers over) the puppy.  
Occassionally, the GSD will also try to nip at her, but we don't know if that's
the way dogs play or if it's inappropriate.  Thanks!

Answer
It's hard for me to say without seeing their reactions, but in general, if you gently remove the dog that you think is being too aggressive in play, one of two things happens.  Either the underdog tries to get away or does not re-engage with the dog, or she goes right back to her playmate.  If she goes back, chances are that everything is ok.  If not, then the older dog might be rough enough that the pup is a bit fearful.
In any case, you would want to socialize the puppy with a lot of different dogs, because you don't want her to only be comfortable with her new housemate, or to think that all dogs are like her housemate - she needs to see larger pups, smaller pups, kids, men, people of color, people in uniform, umbrellas being opened, etc.  Dogs do nip at one another - if no one is yelping that's a good sign.  Most older dogs are tolerant of very young puppies, say up to about 5-6 months of age.  Then, they tend to tell them how to behave LOL.  But, in a normal "pack", it's done gracefully for the most part.  If you have any concerns, my suggestion is to get a good positive trainer to come and observe the dogs so you can be sure all is well.