First consider if you have enough roosting space. Measure it. Secondly, are your roosts higher than the nest? I am assuming that they are, if the older birds are roosting.
Blocking off the nests in the late afternoon is a good idea. I am assuming that you don't have a run attached to your coop? It is always a bit unclear with written posts. I myself rather hate to lock birds in a coop all day in the middle of summer, I worry about excess heat. If I locked them in the coop this time of year, it would be in the late afternoon, with the nests blocked off, then later I would let the layers in just before dark.
However, if they are roosting in the nests, they should be returning to the coop at night? So no real need to round up? If you need to round up, get a long stick, and move slowly toward the coop, with them between you and coop. When they move away from you, you stop, when they stop, you take a step or two until the 'pressure' on them get them to move again toward the coop. If one trys to run past you, extend your arm, and tap the ground in front of her with the stick. I say "Hut, Hut" at this time. By moving slowly, you can actually round them up more quickly with less stress. Have some scratch on the floor just inside the door.
Or another way is to put scratch in the same bucket or can each time, shake it madly and call 'chick, chick' each time you feed. Do this a few times when they are hungry, and they will come running at the sound of that bucket.
As for the layers, my birds love to change their nests once in a while, so set up a nest outside of the coop. Make it a bit dark, but an easy opeinging, put a couple of golf balls in it, and they should use it no problem. Later on, when you want them to lay back inside the coop, this nest should just disappear.
