I usually remove the 175 w brooder lamp at 5-6 weeks, and the night time temps stay in the 50's. They have enough big feathers to stay warm enough at night.
Do remember that moving to the coop, and moving to the coop with adult chickens would be two different dates! I wouldn't recommend putting the babies (out of the brooder) in with the grown chickens until they are closer to 12 weeks old (tweenagers) (big enough that a peck on them from a grown-up isn't going to cause serious harm). When you do introduce to the adult chickens, there will be disruption, and pecking order will be established. They don't call it pecking order for nothing!
I think the recommendation is closer to 16 weeks, but I personally don't wait that long as they outgrow their brooder (which does have a roost). The brooder pen is located inside the regular pen, so they see each other all the time, so it isn't as big a change for them when they do become one with the entire flock.
Chick food is also different than layer food.
