Taking a day off from school to catch up on the massive amount of homework given during the junior year of high school. Procrastination, multiple research papers, and near-mental breakdowns are usually the precursors to this activity. This term's namesake is derived from the name of one of the top AP English teachers in the world, Ms Roeser, who is notorious for giving large amounts of work. Despite this fact, "roeser day" is used interchangeably to describe a large amount of work given from any teacher.
Student 1: "Danggg, we have seven research papers due on Wednesday!"
Student 2: "I can handle it."
Student 1: "Oh yeah, AND a vocab quiz!"
Student 2: "OK THAT'S IT I'M TAKING A ROESER DAY."