More information is needed. How many birds have you lost? Did they all disappear at once or over a period of time? Did you lose them during the day or at night? Do you free range? If you are losing some to predators do you have any idea what you are up against?
If you are losing them at night a rooster won't help at all. They also only offer limited protection during the day, if any protection at all. I know some have had success with a rooster vs a hawk, but I have not. They also cannot stop the larger predators such as dogs, foxes or coyotes. If you are losing them while they free range, you would have more luck penning them up util you know what is attacking them. Or investing in electric fencing.