You probably upset them ,the one you killed could have been the favourite aunt or uncle to thousands of juveniles, they are now living with the idea that size 7 shoes are on a mission to wipe out all there relatives, the thought of there being no-one to babysit them when there parents are out for a night on the tiles (or carpet) must make them extremely angry ,so my advice is to leave them alone ,remember they are the food for hedgehogs rats bats and birds.

It has less to do with killing one and more to do with you had a roach infection in the first place, probably. Get an exterminator to spray around your house to get rid of them.

More like, you kill one and a billion would hide from you producing 10 billion more.

that means that there's a nest in your house somewhere and that that nest has been "disturbed";call your nearest exterminator.

I really hate roaches, and ever since I killed one like a billion started appearing. Its actually freaking me out and I don't know what to do because everytime I kill one more, and more keep appearing. :O