Puppie playing with dog

Question
I have a 15 month old yellow lab (Sandy) who is very hyper and loves to play with everyone including dogs.  About a week ago I brought home a chocolate lab (Rocky).  Sandy and Rocky plays together consistently.  How do I know if they are playing to rough and if they do get to rough how do I stop them.  Also we have had some trouble potty training Rocky (I think that this is because they are playing consistently).  I put Rocky in a crate during the night and while I am at work.  After 4 hours I will wake up or come home from work to let him out but he always seems to have pee in his cage.  The cage is a smaller cage and he can turn around and stand up but that is al the room he has.  Is there anything that I can do?  

PS.  Are male dogs hardier to train then female dogs?

Answer
I amazed at how well older dogs play with puppies.  An occasional yelp of pain is no problem if the bigger dog lets up quickly.  I wouldn't break things up unless it looks like the little one is really trying to get away, and doesn't come back.  As long as they come back for more, they aren't hurt.  If not, maybe pop Rocky in his crate until things cool off a little.

Being too busy playing to ask to go out can be a problem even with puppies a few months old.  We see it a lot when friends or family come to visit.  The trick is to get a feel for the timing, and take the puppy out.  I am no believer in schedules.  I say learn to read the puppy.  The page can go blank with another young dog to play with.  You may have to run Rocky out about every half hour.  

I haven't had problems with leaving 2 month olds in a crate 4-5 hours.  Some say that is too long.  Mention it to the vet next time you are in for shots.  In the mean time, add a rack to the floor of the crate.   Skip the
bedding.  At first it gets wet, and later it can be chewed into choking
hazards.  A wire rack in the bottom will help keep the puppy up out of
accidents at first. They are available with the crates, but a piece of closely
spaced wire closet shelving from a home supply place is cheaper.  I have been doing it for years until the puppy stays dry in the crate consistently.  

Puppies vary.  I don't remember having more trouble with the males than the females.