Hi and thank you for using Just Answer.
This warning is indicating that the roller's bristles are worn to a point that brush agitation is less effective. To remove this light try to clean the roller out first. Remove hair and other debris from the roller, Once you have done this, reinstall the roller. If the light still comes on, then you'll have to replace the roller. If you have any other questions, please let me know. I wish you the best.