For over 15 years, there has been a Carrion Crow roost at University. In winter, I used to leave work when the crows started to gather on a large poplar tree to spend the night. Each arrival being greeted with raucous calls. I found the atmosphere amazing as their vocal repertoire is so diverse: gurgling, croaking, trumpeting, beak drumming, almost quacking, compounded by the often different tone of voice of different individuals. Tonight, I happened to be by the roost at the right time again. At least 50 crows were already assembled on the top branches, leaving respectful spaces between them, members of pairs closer to each other, and, as I was approaching, pairs and bands of crows flew over me to settle on the tree.
Crows can fly long distances to roost in their traditional trees (I have read up to 50 miles for American Crow). It can be well past sunset when they settle and they leave first light in the morning. When the nesting season starts, around March, territory holders stop roosting communally, while non breeding birds might carry on sleeping on the traditional roost.
I took this little video of tonights' crow night-time assembly.