Roll numbers are generally issued about 15 days before start of exams. These roll numbers are published on IEI website http://www.ieindia.info/ or you can view these roll numbers on http://www.amiestudycircle.com/ at appropriate time.
You can also take print of admit card and use this with identity card in exam hall.
Printed admit card can be obtained from exam hall/or your centre.
For a list of exam centres, click here