What are these “finial” looking things mounted to the roof area of homes on the East Coast [SOLVED]

They are ice and snow catcher things. They come in different forms, sometimes bars and these new versions in your picture. They hold the snow and ice in place during the winter.

Ice and snow will build up and weigh a ton, sometimes literally, and that weight falling on someone could easily kill them. With this system you are far less likely to have the entire sheet come down and it lets the cold stuff melt on the roof instead on people's heads.