what will happen if you forget to write your name and roll number in your jee main rough sheets

Dear Aspirant
The rough sheets given to you in the JEE Mains entrance examination are just for your rough work. It has nothing to do with your selection You are told to write your name and roll number on them in order to avoid cheating that is getting the sheets exchanged by other students. So if you forgot to write it's not at all a matter of concern. The point is you should focus on your work only.
Hope it helps
All the best