They can be really aggravating can’t they? At that age and with those breeds I’d have expected them to start roosting by now. The roosts look fine. I don’t know how high they are but they look like they are high enough they should be using them. Since you don’t have Silkies that can’t fly and those roosts are plenty open so they can get to them, I don’t see a problem with the set-up. I’ve used tree limbs, 2x4’s flat side up and 2x4’s narrow side up a lot higher than those. I find people care about the shape and size of the roosts a lot more than the chickens do. You can try putting some more roosts up higher or change those to narrow side up but I really don’t think that will make a difference. You are dealing with chickens though. Their bird brains don’t always follow the same logic ours do.
There is nothing wrong with them sleeping in a pile on the floor other than the poop might build up and you have to “manage” that with a shovel. Normally if one starts to roost the rest soon follow but you have to have that one willing to start. My brooder-raised chicks normally wait until 10 to 12 weeks to start roosting though some have started around five weeks and some have waited a lot longer. 14 weeks and not roosting is not unreasonable. They could start on their own at any time.
If you want to teach them to roost, make sure the coop is very dark, no lights inside and maybe block the windows at night if you have lights outside. Then just set a few up on the roosts after they are asleep. You don’t have to put all of them up there but if you know which are the most dominant ones those are a good choice. They might catch on after a time or two of doing this, you may have to be patient and consistent for a while.
Good luck!