Personally I would not use PVC. It’s too slick plus I’d have some concerns it might be too cold in the winter. Wood is a good insulating material. It will not drain heat away from their feet. I much prefer wood over anything else.
Bumblefoot is not corns, it’s an infection. They can get bumblefoot by cutting their feet on glass, sharp rocks, something like that. Also a splinter or briar thorn can cause it. I would not worry about them getting bumblefoot because of pressure from what they are sleeping on. If you use a sawn board (2x2 or 2x4) as a roost I’d sand off the corners. Round them off, partly to make it easier on them when they curl their toes around it but mostly to remove splinters.
From what I’ve seen, people worry about this a lot more than my chickens do.
I do recommend you use wood, not PVC and especially not metal. Whether you go flat side, narrow side, or round you will please some people and horrify others. From what I’ve seen with mine your chickens won’t care. Just round off the corners.