We're assuming that you're giving full disclosure about your reasons for re-homing these roosters, that the folks reading & replying to your ads know it's a rooster that's been aggressive & has already injured a child. It would not be fair to pass on a problem bird without advance warning.
To answer your question, no, not all roosters flog. The ones I keep do not. But I am still careful when small children visit the yard and don't take the rooster's good manners for granted.
Since there really are barely enough opportunities for 10% of all roosters hatched to find positions as pets or flock husbands, it doesn't make sense to keep human-agressive roosters around. It's great that your little girl enjoys your chickens so much, and wants to take part in their care. You need a mannerly flock for her sake.
I wouldn't depend on the roosters to stand up & protect my chickens. Roosters are best at sounding the alarm when danger threatens, not at fighting off predators. You just need one who is alert, not one who is aggressive. Instead, provide hiding places for your free-ranged flock, and good fencing around your coops.