I agree with the other posts. If you want to add a new roo you may have to put the new roo and some girls in a different pen. The only success I have had with having two or more boys in one pen is if the pen is large enough so the subordinate boys can get away from the dominate boy and they grew up together. It has been also that time of the year when the boys aren't doing a good job. Fertility should pick up as the days get longer and warmer.
Also too even if you can get two males to get along in a pen with hens. The dominant male is going to do his best to knock the other off the hen while mating. It is survival of the fittest at it very best only the strong survive which means they WILL make sure of that.
Jeff