This sounds like your first year. Roosters are a crap shoot, and take experience. Multiple roosters just drastically increase the odds of having a wreck. Just leave things as they are right now, and get some experience.
Personally, I find having a rooster really does help, but they are chickens. Nothing is fool proof. If you have predators, you are going to get hit, more than likely. Lock up for a few days.
I think adding another rooster, would cause more problems than it is worth at this point. If you free range, you will have birds leaving the flock, so at that point you can add new birds. But I don't think adding another rooster will prevent free ranging losses.
Mrs K