That's perfectly normal behavior. You have unsupervised teenagers out there, boys and girls, with hormones running wild. They do not have human morals but rather chicken morals. Those are different.
Those roosters and pullets are coming into maturity. The roosters' hormones are telling them what to do. Some of the pullets are probably cooperating and some are probably resisting. That's normal too.
Part of it is mating, but another part of it is that the mating behavior shows dominance. Those roosters are not only trying to make sure any egg that gets laid is fertile like they are supposed to do, they are also trying to establish dominance over those pullets.
In flocks that don't have mature roosters, the dominant hen will often "mate" with another hen, going so far as to touch vents. She's not bent or weird. She's just demonstrating that she is dominant over the other hen. That's part of what your roosters are doing, but a bigger part if it is mating behavior too due the the hormones the roosters and pullets have running wild.
I've seen this behavior when the pullets were way too young to lay so it is not an absolute guarantee, but this is a pretty good indication that eggs are in your near future.
Good luck and enjoy those eggs.
