Hello-
Sometimes it's really hard to tell exactly who's a roo and who's a hen with chicks. You would look for signs like, bigger combs and waddles(wattles?), bigger legs and feet, alot of chest bumping and pointy hackle feathers (around the neck), and sometimes you can see the longer, more colorful tail feathers developing. Also, sometimes a rooster can take longer to feather out--keeping their baby fuzz longer than the females.
It's ok to put them out, if temps are right, and roos usually don't start crowing very early......I've had several roosters now and sometimes they don't crow until they look almost full grown, other times, it's a little bit earlier.....
Hope this helps,
Sharon