Roosters can sometimes protect hens from Hawks and other attacks but not all Roosters will do anything to protect the hens or chickens from attack.
Sometimes you might have to shoot the Hawk if it does attack your chickens and if you do need to shoot the hawk to defend the chickens then you can legally do so.
I would also recommend putting some wire over the hens and chickens coop to prevent the hawk from swooping down into the hen and chickens pen and scooping them up.
But having a rooster or two roosters along with the hens or chickens can help sometimes protect them from the Hawk but not always.