Roost is optional. I haven't done this, but I have a big wire dog cage I could do it in. I would not put a roost in it, myself, but don't see any harm in it, either.
Yes, please provide food and water in the cage. No reason to deprive her of these. The point is to put her where there is air flow to her bottom side, which does not feel like eggs and a nest, which is supposed to trigger a change in her hormones. Just do NOT put any straw or hay or anything else like nesting material in there.
You're on your own with the poop! Hopefully, the mesh will be big enough that most of it will fall through.
I gather from reading that the key to when it has worked is that she gets restless and acts like she wants out.
I did cage my broody part of the time she was setting, much as I dislike the idea of caging, not to cage her in, but to cage the other hens out. I firmly believe she was grateful. Broodies don't want to go anywhere, they want to be left alone, and not have other hens trying to lay where they are setting. I let her out every morning, because she would stand up when I opened the coop. I tried letting her out other times, but the best I could do was get her to eat a bit of fruit from my hand in the afternoon; she would not get off the nest to go out and eat and such again. (I had water and food in the cage, of course, but it never looked like she touched them.)