Chickens don't like to hold onto a roost, they like a flat surface to rest on. The wide side of a 2x4 is just right. I made my roost like yours before I joined BYC. When I read that, I added a second board to make it the right width.
They should be about ready to lay. Their combs will turn...
There's a lot of variation in when they will lay. Some breeds take much longer than others, and some individuals in a breed take longer than others. What breed are they?
What is the roost made of? Maybe it is not comfortable for them.