1. people will be punished severely for something
if that task isn't done on time, heads will roll!
The expression heads will roll refers to severe punishment and perhaps comes from the use of a guillotine to behead people during the French Revolution. When you say heads will roll it means you expect some people to be punished or to be in line for a severe reprimand. This idiomatic phrase is often used hyperbolically in reference to people being fired.