The only reason you need a rooster is if you want fertile eggs. Everything else is personal preference. Nothing wrong with personal preferences, I have a few myself, but those are choices, not a need.
What are your goals with chickens and how does having a rooster fit in with those? My general suggestion is to keep as few roosters as you can and still meet your goals. That's not because you are guaranteed problems with more roosters, just that the more you have the more likely problems are. For many people the best number is zero.
I've had several predator attacks by dogs, fox, hawk, and owl. In none of those has the rooster lost a feather. I find him cowering in the coop on the roosts with the rest of the survivors. I've had several different roosters over the years. Mine haven't sacrificed themselves to defend their flock, they lead them to safety.
A good rooster will be alert. He scans the skies looking for birds of prey. So he can be an early warning system. But not all roosters are good. Usually the dominant hen takes on these duties if the flock does not have a nature rooster. I consider this to be of limited value. There are many people on this forum that have free ranging flocks that are all hens, no roosters around. Others would not dream of having a flock without a rooster. A lot or personal preference.
One thing my roosters do is when something suspicious is going but they aren't sure, they warn the girls and put themselves between the flock and whatever is going on. They don't necessarily go check it out but stay between the flock and whatever it is until they decide it is OK or they need to lead them to safety. That might be a ground-based predator like a fox, it won't be anything flying. Anything flying is an alert. Usually it's something like a piece of paper blowing in the wind or me carrying something they aren't used to seeing me carry, like a camera.
Overall I give very low points as a flock protector but they are not totally worthless.
A rooster does not have an effect of whether a hen lays egg or if she goes broody. No pros or cons there.
The pros and cons are not always clear. A lot depends on whether or not you have a "good" rooster. A "good" rooster does not depend on breed, it depends on the individual rooster. You can find good roosters and horrible roosters of any breed, whether that is Sussex, Silkies, Rhode island Reds, or anything else.
A good rooster helps keep peace in his flock. A bad rooster either ignores this or attacks and beats up the girls. A good rooster does not over-mate his girls or rip off their feathers when he mates, a bad rooster will. A good rooster may find food and let the girls eat first. Not so with a bad rooster. A good rooster does not attack humans. A bad rooster can inflict injury, especially to younger kids. Some roosters ignore kids but some stalk them and terrorize them so much that they can't play outside if a rooster is around.
If you read enough threads on this forum you will find examples of all of this and more, both good and bad. If you pay attention you'll see that breed doesn't matter.
Other than fertility the reason you might want a rooster is simply that you want one. Any perceived benefits may be there or they may be a liability, depending a lot on whether he is good or bad. Quite often a rooster is good in some things and bad in others.
