can any one help i have a 4 month old rotty male and a 7 year old female bullmastiff and the pup is constantly wanting to play fight  with bullmastiff ,bullmastiff will play for a while and then want to stop but the rotty will keep on at her constantly .i feel real sorry for her because he will bite at her face and make her yelp .i tell him off and put him in his crate for time out but to no affect as soon as he comes back out hes straight back on her again any advice would be welcomed.

My Advice after having been on a good training course.......

Separate them. Allow only supervised play time until he has some manners. he is being a bully and if allow to keep this up you will quite possibly end up with a dog who bullies or fights with other dogs. Get him focused on you. Any time he plays it is with you and not another dog. 4 months is not too soon to start learning how to behave.  Telling him off and time outs( as you see for yourself ) do not work. If you are consistent in keeping them separate when you are not around and him on a house line and supervised he will soon learn how to be good with the other dog. They can socialize but not play.....You are his new best friend not the other dog.
Just my 2 pennies worth...I am sure more will come along to help as well.

I may get it wrong.....so use what you want then throw the rest away...:-)

Your pup is not being a bully, he is being a pup that likes to play rough, but unfortunately when they are with an adult dog that is very tolerant they don't learn the rules. Don't stop them playing altogether, just step in when the older dog has had enough or you think the pup is being too rough.
I have a Mastiff pup (who's 9 months old now) and an old male lab cross, my old dog is very tolerant and will not tell the pup off enough so I just step in when I think the pup is being too rough and distract him with a toy. The pup is finally getting the message, if he is trying to play rough with the old dog a 'no bite' or 'get toy' will mostly help. Another thing that helps is to encourage the dogs to play with a toy together, that way the pup can play with the adult, but by biting on a toy instead of the other dog.
I've personally found that 'time out's' are of no use in this situation, the pup is wanting to play so it's best to encourage him to play with something other than your older dog when he wants to rough-house, this is playfull energy that needs redirecting rather than stopping completely. It wont happen over night but eventually your pup will learn that rough playtime is for toys and not for swinging off your other dogs face. My pup was just like this too, he still needs reminding occasionally, but that's more to do with the size difference now as our old dog is a lot smaller than the pup, so even 'gentle' play can be too much for the old dog.

I have also found that as my old dog has learnt that i will back him up/save him from the pup he is a lot more forth-coming with his own reprimands, it's almost as if he was worried about being told off to start with, but as he sees me stopping the pup being rough it seems like it's given him the all-clear to do the same.

Your pup is not being a bully, he is being a pup that likes to play rough

Yes, exactly!

So many people do not understand that this is exactly how pups play, which is why I do not sell a pup to anyone with very young children, people have the image that pups are cuddly and sleep on your lap, they do, but they are also little monsters who would happily rip the clothes off your back if not properly supervised. :-D

Just make sure that your 7 year old has plenty of escape time, also when pup is playing rough don't always put in the crate, take over the play and re-focus really rough play to play training, retrieve games, hide and seek, tug games, take your pup in the garden for play just with you. Not only to give your girl a rest but to help bond with it's human too.