My two play rough and tumble with eachother on a daily basis... Sometimes Duke can get kinda annoying to Mia though so I will let her out alone to get some one on one play time without getting harassed by Duke the whole time. He will run up behind her and do the whole body slam thing or bite the neck really hard thing. She may make a yip which I dont like but about 2 seconds or less after that she is up and kicking his butt!
But then I try to tell them enough depending on the situation and so they know that I am still the boss.
Just keep a eye on them to make sure no one is getting REALLY hurt. It has not gotten to any over aggressive on our end and they have been playing that way for 2 years...