how many roosters do i need?

Id say you need about 3 or 4

 

With 14 hens, you might need 2 roosters...but really one would do the job. Just your fertility rate might not be 100%. Usually 1 roo for 10 to 12 hens works fine. What breeds are you looking to have, in hens? I might suggest a Buff Orpington rooster. Mine is very gentle with the ladies, and doesnt mind me picking the hens up at all!

 

With 14 hens one roo could do the job, but two would pretty much make sure all the hens are "covered"
It would help your fertility rate.
If they free range the possibity of fighting is decreased but at all times one will be dominate and tend to chase the other off and yes they might fight.
I can't say I've had any "bad" roos from any of the standard breeds that I have raise. Well, "bad" toward humans, but I've had a few that were a little rough with the hen and I think this occurs a lot when the head roo is a good one and always on the lookout and especially if the head roo is overly protective of the hens when others try to mate. I've seen some roos charge from 25' away to "hit" another rooster mating a hen. Looks like to me the younger/less dominate roos will be more aggressive because they are being faster at trying to mate because they know "he" is coming.
Roosters have personalities too. Most of them are good but you can get a "bad apple" from time to time.

 

Unless they free range more than one roo in the coop is too many. He may do fine with 14 girls.

If you get another roo you will need 2 coops in most cases.

Some roos get along in one coop but they don't really make nice. As they get older and older they get dominant and aggressive and some day you may find bloodshed in the hen house.

There are people who have several roos and they get along fine but this is not normally the case. I am not trying to scare you but to just let you know what to expect when things are not near to perfect.

 

One rooster is plenty and would guarantee you have no fighting problems. It is always a crap shoot with roosters some will get along others won't.
If you are just planning on having one flock and aren't planning to have to seperate breeds then I would sau one is enough. Plus having to deal with just one roo will be less stress for the hens.

 

1 Rooster would do the job... BUT I would order 2 because if something unforseen happens to one you are still roosterless
I think if you raise them together they stand a much better chance of getting along.