Thank you for coming here to get the true story. It really is amazing how folks mis understand bird's reproduction.
It is kind of ironic, though, that other folks will swear blind your hens won't lay unless you have a rooster
Hens ovulate and form eggs regardless of the presence of a rooster. If a rooster is present, chances are your eggs are fertile. When he mates with a hen, she stores the sperm internally and the eggs are fertilized as the egg is made. One mating can give her enough sperm to fertilize a good 2 week's worth of eggs.
It takes quite the practiced eye to tell if an egg is fertile. If you do a search here, you'll see multiple threads about "Is this egg fertile".....it's hard to tell a lot of the time, even when we're looking for it.
With a fertile eggs, development of the embryo doesn't start until it's been incubated at about 100 degrees for 3 days. So, as long as you collect your eggs every day or so, you'll be fine.
I've kept roosters with my layers all my life. Except a memorable time when i was sick and the kiddos were caring for my flock and missed a broody, I've never once had a nasty surprise when I cracked an egg.
Now, having your own backyard birds, you're likely to get blood or meat spots, and those freak folks out, thinking they're baby chicks. They're not, they're simply glitches in the hen's reproductive system. In commercial eggs, those are candled and pulled from the shelves, so consumers never see them. Folks don't realize how common they can be, especially with new layers.