To save time, she bought pre-rolled sushi nori sheets.

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。pre-rolled 字面意思是“预先卷好的”，用来描述已经卷好的寿司海苔片。