Can females hold sperm???

Today i opened an eggs sack... rather then waiting for it to hatch... i know thats wrong. But almost all of them came crawling out. My question is... I had two female roaches, and one... well it escaped about 2 weeks ago... and the other one seems very young and i don't think this is her eggs sack... so my question is... how long to eggs sacks take to hatch after being deposited?