Some will try to defend hens. Results very much a function of threat. With most mammals, rooster is taking a very serious risk especially with something like fox or dog. Best defense my rooster provides against fox is that he provides loud-showy diversion that distracts predator but rooster will fly when predator gets close. With respect to hawks sometimes roosters activities more along lines of proper defense. My game roosters when free ranged with adequate cover and not in molt will attack a hawk if latter follows flock into heavy cover where hawk cannot fly. Same roosters will also take Coopers hawk on in open to protect his chicks / juveniles. With chicks he also has aid of their mother.
In my experience defense is actually in chicks, not hens.
Some of the "defense" many folks refer to is simply signal to flock that a ground or avian predator is present. Call can also indicate type and threat level presented by predator. Call may also signal to predator it has been detected and should go elsewhere for easier pickings. The rowdy cackling, especially when chicks are involved may also distract predator as it certainly works on me.
The business of shyness has not been for a predictor of anti-predator activity for me. Age, breed, and stage in molt cycle much more important.