Being a good observer and knowing when to sound warning calls is not only an individual thing, but also has to do with age. When birds are younger, and do not yet have much experience with predators (especially when not raised by a broody), they tend to spook very easily, even at the sound of a dove. With age, they get better.
As long as the rooster doesn't have any feature stopping it from doing its job as sentinel(as is the case with most polish roosters and their enormous crests that reach their eyes), you should be good
As long as the rooster doesn't have any feature stopping it from doing its job as sentinel(as is the case with most polish roosters and their enormous crests that reach their eyes), you should be good