This will help as I'm new but this worked great. Near dusk coax one of them up the ramp, get one or two in and the others will follow. After a day or two they will be automatic. Next, the problem with them laying on the floor is probably because they are waiting till it's too dark inside and then they cannot see to roost so they just lay on the floor. I solved this by leaving the large door open and they gave them just enough light to get settled in.
I still have one that waits till the last second so I've started shining a light in one of the windows to all her (or him) to get up, then I turn the light off. As soon as I gave them a little more light and made sure they knew where the roost was I've never had them sleep on the floor again, mine are almost 9 weeks old now.