In cases where the machine encounters discrepancies (like unbubbled roll numbers but a written roll number), there's a possibility of manual verification by officials to resolve the issue.

Your OMR sheet may have other details like your name, exam center code, or other information which might help in identifying your paper even without the bubbled roll number,so dont worry..

If you’ve written your roll number in the given space but forgot to fill the circles, there’s a chance the OMR sheet scanner might not read it automatically. But don’t worry too much usually, during evaluation, if something like this is noticed, the exam staff or invigilators cross-check the written roll number manually. It’s better to inform the university or exam cell as soon as possible, just so they are aware. Most likely, it won’t affect your result if your details are clearly written and readable.