Ryan is right. The roller brings moisture to the surface and there it dries. Batting first might be ok for a few overs but once the moisture and subsequent drying takes effect it should do a fair bit. If you wanted to bat first then don't roll it and it will behave like a pudding for a while longer.
Regarding rolling, that's why there isn't much point rolling a dry hard deck. You only roll a wicket when you can press your thumb into the surface, a bit like plasticine.
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