A proposal to leave or take off in a group, usually prefaced by "let's;" combination of phrases: "let's roll" and "blow this joint;" connotes the desire to move on.
Other possible use: to earn money (i.e. make this paper)
Yo fellas, let's roll this joint. My shorty ain't havin' none a dis.
I'm flat broke, dawg. I need to roll this joint.