He bought some pre-rolled joints so he wouldn't have to roll them himself.

pre-rolled 是由前缀 pre-（表示"预先、提前"）和动词 roll（"卷、滚动"）的过去分词 rolled 组合而成的形容词，字面意思是"预先卷好的"。 joints 是名词 joint 的复数形式，在这里特指"手工卷制的香烟"。 pre-rolled joints 指"预先卷制好的烟卷"，使用者无需自己动手卷制。