The best roosting area I've seen is no longer available to the crows - it was an "empty" lot next to the building I worked in, in a far west suburb of Chicago. The trees in that lot held hundreds of crows during the winter months. The noise was amazing! iIt was fun to watch them come in to roost.
it wasn't far from farmer's fields, and a small pond was nearby as well. Possibly the dumpsters behind the building I worked in had some attraction as well?
Crows are amazing - i love watching them.