I think that you should be able to let them roost next week. Mine are 6 weeks old now and their roost is only about 3 inches off the ground, too high and they can get leg injuries when they are so young. Also, don't use plastic or metal for your roost because it is too slippery. It is so precious to see them roosting when they are still so little ....instincts are funny.
I put in a roost the same day they come off the towels... so Day 4 I guess. It's an inch off the ground. Then when they first start flying around... about a week and a half I add a second higher perch that can be adjusted. Mine are 2 weeks old today and the high perch is as tall as they are so around 4-5 inches.
My Hubby made a little three inch roost on a platform with a little cross piece (I'll post a pic) for my brooder and three of my 7 Black Jersey Giant babies were snoozing on it week one - now I don't know if you could call it roosting, because I know they also sleep in a clutch. They're two weeks old now and I know four of them line up on it, one with her head tucked under her wing... (yes, I know... pictures pictures - working on that
I just put a smaller piece of my oak firewood in with my chicks, it's about 3 inches wide, about a foot long and maybe 2 inches high and the 2 week old chicks are always on it, they love it and they dont try to balance on the waterer anymore. It's big enough to hold their weight, get them a couple inches off the ground but not so big that it takes up a lot of space.
Yes that's my dogs nose in the picture checking out the chicks and their roost!
I put a dowel in when they go onto shavings, the first several days it's just above shavings level, while they learn to balance. After about a week and they're popping up, flapping and trying to fly, I raise it to about three inches. As they get older I add higher ones.
If I don't put in dowels they roost on the waterer and the feeder - ick. It's hilarious watching something still downy and without a tail yet, trying to balance and sleep on a roost. They're so sweet and awkward.
I discovered with the first and second batches, no roosts means more mess and more sparring. Neither I like.