I don't play rough with Banjo myself because I am fragile and never liked rough and tumble games anyhow. And I would've never thought my daughter would be able to because we had to go through such great lengths to stop Banjo beating us up in normal situations when we got her, with all the exuberant jumping and mouthing she did. And there are many times when I look at them playing and I tell my daughter that it is going to end in tears. And I think that sometimes makes her push back the tears when a paw or tooth does land in the wrong spot (because she hates admitting I was right). Which is great because she used to be a bit oversensitive to pain. And she will cry if the dog hurts her when they are NOT playing. Which makes Banjo quietly retreat and look all sorry.
So I would not want to stop the playing, because I think they both get so much out of it. And I promised my daughter that we would get a dog she could play with. And I think she has a right to define her relationship with the dog herself - up to a point.
But what you say about showing the dog that you will stand up for them is useful. Not sure how if I can apply that in this specific situation, but I will definitely think about it.