Already roosting at 5 weeks!!! You are doing well!!! Mine often don't start roosting on their own without a broody to show them until 10 to 12 weeks. Each brood is different. Welcome to the forum, by the way.
When I started my flock I never blocked the nests. Now that I have laying hens in my flock I am not going to block the nests though if I wanted to work harder than I need to I could. I just don't see the benefit.
If chickens are sleeping in the nest there is a reason. One typical reason is that the nests are higher than the roosts. Another typical problem is that bullies are beating up some chickens on the roosts so the ones being bullied look for a safer place to sleep. Or maybe you just don't have enough roosts. Or maybe they can't get to the roosts, usually because the coop is too constricted so they cannot spread their wings to fly up or down. If chicken are going to sleep in the nests I want to know it before I start getting poopy eggs so I can fix the problem.
I don't know how many chickens you have, what your coop, nests, or roosts look like. My generic suggestion is to unblock the nests and see where they sleep. If you don't have a problem, you don't have a problem. Why fix a problem that you don't have?
If you do have a problem come back with details and we can discuss how you might fix it. That might be to raise or expand the roosts. That might be to block the nests in a way that is not higher than the roosts until they get in the habit of sleeping on the roosts. That might be to set the birds on the roosts after it gets dark until they get in the habit of sleeping there. It may be something else. We all have unique situations and what works for me might not work for you. Before I suggest a specific route I like to know what you are working with.
Any possibility of raising the roosts. Chickens generally like to roost at the highest point possible.
