There are many things to consider before adding a rooster to your flock. The first thing you need to find out is if you are allowed to have one. Be sure to look into the by-laws in your area to find out if you can have a rooster on your property before any other consideration.
If you find out that you can indeed have a rooster, the next step is to decide whether having one is right for you.
Pros
Fertile eggs – if you have a rooster, you won’t need to buy hatching eggs or worry about shipping or other problems that can come with buying from an outside source when you have your own. Just a note: fertile eggs do not taste any different from non-fertile eggs and they are just as safe to eat as an unfertilized egg.
Protection – a rooster makes an excellent guardian for his hens. The rooster will warn them when he sees danger coming, will lead away or even fight predators, and will keep the hens in safer sections of their environment.


(Note my rooster is keeping watch while the hens forage)
Management – a rooster will often keep his hens in line, preventing fighting and other problems. He will alert them to any food or water he finds and will often leave them to eat what he finds while he continues to search. When I had some hens that had never been outside before, my rooster also showed them how to forage and what to eat. I once witnessed my rooster with five of the six hens in the tree line. He noticed that the sixth hen was across the yard in the other shaded portion and he ran over and chased her back to the group.
Expense – because of the large number of roosters in most areas, they are often much less expensive than hens.
Size – roosters are larger than hens, making them ideal to raise for meat purposes.
Looks – Roosters often have more color and ‘presence’ than a hen.

Cons
Noise – a rooster will crow and not all of them have a nice sound to them. Different sizes and breeds have their own sounds and it can be very irritating to you or your neighbors. It isn’t just a one time a day action either. My rooster crows intermittently from morning until late afternoon.


(My rooster crowing. Also note the visible spur on the left)
Spurs – not all roosters have a nice personality and if you get a nasty one that wants to attack you, it will hurt. There are things you can do to prevent attacks and manage them, but you will have to consider the safety of yourself and others that may visit or come on your property that may be injured. The older the rooster gets, the longer the spurs get.
Damage to hens – The rule of thumb is one rooster for every ten hens. If you have only one or two hens, they will likely have feathers missing on their backs from the rooster mounting them. Their laying may also suffer from the stress of the rooster chasing them around. If you have more than ten hens, the percentage of fertility is more likely to go down.
Aggression – more than one rooster will fight over the hens. If you do have two that don’t kill each other, they will both be so busy keeping the other one from breeding that there’s a very high chance that your eggs won’t get fertilized.

Other Considerations
If you are getting a rooster for breeding purposes, make sure you look into the breed you are interested in to find out what kind of temperament you can expect from that breed in particular. While not all roosters will follow the breed norm, it’s always best to know what you are potentially getting before you decide to get a breed known for aggression.
Roosters also enjoy flying and roosting higher than hens, so keep this in mind when building a fence and coop for your rooster. Clipping one wing or having an enclosed run are some of the options available.
As with any other animal, please do your research and find out what is best for you and your situation before you bring it home.