To get super crispy brussel sprouts, a high oven temperature is essential. Always preheat your oven before roasting brussel sprouts. Secondly, ensure each brussel sprout is well coated with oil, this will help them to soften and get crispy. Finally, don't crowd the brussel sprouts together on the sheet pan. Spread them out in an even layer to help the air circulate and crisp each individual sprout.