how old do my baby chicks have to be before letting them in the coop with the bigger chickens and roosters

That depends on how big & aggressive ur chickens are. If u have smaller, tame roosters & hens, try letting them out at about 6 or 7 weeks. Put them in at NIGHT when they r all roosted down & ready for bed. Then they r more likely to accept them.

If ur chickens r more aggressive, or do not accept them, wait another week. You could also try just putting them in at night & then taking them out again during the day, untill they get used to one another.

Good luck!

If you have the mother, she usually takes them out and about in 3days. If you do not have the mother, I would wait longer, until they can regulate their body temp.