Hiii

AMU authorities will provide a correction facility in the month of March to make chnages in the application form.
The candidate will be allowed to make corrections in the following fields - Name of Candidate, Father's Name, Mother's Name, Date of Birth and Gender.
I dont think you can change the roll no once you have submitted it. So i would suggest that you reach out to the authorities itself and inform them about the issue. So that they can help you in solving it.
Mail them your query or reach out to them by calling the customer care helpline number.

Hope this helps
Thanks!!