Blanching brussels sprouts before roasting them can help them become tender faster. To blanch brussels sprouts, cook them in boiling water for 2 minutes, drain, and immediately place them in an ice bath for 5 minutes to stop the cooking. While this step does help to tenderize them, it is an extra step and is not absolutely necessary. I prefer to eliminate this step and just cut the brussels sprouts in half before roasting to ensure they cook through.