None of my non-chicken raised chicks would roost at night until they were around 12 weeks old or so. None of 'em. The broody hen hatched and raised chicks got up with Momma around six weeks of age, just to stay with her when SHE returned to the roost. Another broody tried to get her chicks to roost at five weeks but ended up every night on the floor with them until they finally managed to roost with her one night. It took her about a week to train 'em.
So, six weeks or less with a momma encouraging them, twelve weeks without.
It's not a big thing at all that "they won't roost at night."
As for egg laying, you've got some time left before you have to start worrying about that situation! Young layers often take a few days of laying before they figure out the nest box is the best place for eggs. Many of 'em are startled by the need to lay an egg and drop their first few eggs wherever it happened. "Buh-bawk! An egg fell out of my butt! How odd!" And off they go, after laying their eggs on the coop floor, in the run, maybe in a corner of the coop. Even after they start laying IN the nest boxes, they'll still announce the now-familiar event after they get out of the nest and go on their merry ways.