If you do not know for a fact that the rollers are broken, the first thing I would suggest is try adjusting the screen door rollers and see if that helps them roll better. Take a look at the video below; it shows the most common type of adjustment for screen doors.
If adjusting the rollers does not work, you may indeed have to replace the roller system. I cannot tell you exactly what rollers you will need. Your best bet is to remove one of the rollers and take a look at the screen door rollers available and You should be able to find the proper rollers for your door.
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