The roost that I have on the easter egger pen right now is a sawhorse that sits in the very center of the pen, away from all of the edges. That's perfect for them, since most predators are likely to get them either late at night, or in the early hours before they actually jump down from the roost.
My silkies don't really roost. They all stay on top of or in the nest boxes, that are only about a foot high. But there again they sit in the very center of the pen away from the outside edges, so predators can't get them very easily. I try to keep things away from the edges for that very reason. So if the concern deals with predators reaching through, I'm not worried at all. If the problem is predators tearing it up and getting inside completely, then I have reason to worry.