Okay here's my try at explaining what rolling over your feet is. If you are standing in first position it should look like this:
www.myphysio.ca/site_assets/images/ballet_b.jpg
but some people don't have the right body or strength to point their feet straight to the sides and end up compensating by "rolling their feet" like this:
http://www.myphysio.ca/site_assets/images/ballet_a.jpgBasically what's happening is that you are putting your weight in the incorrect position, towards the front of your foot. To fix this you should bring your position in a bit (less 'perfect' I guess you'd say) and slowly work on making your weight stay in the middle of your foot and your arches up and off of the floor as much as possible. I hope that helped
smile If that doesn't help much look at this site it goes over all those basic pesky things you might have problems noticing, but your teacher keeps pointing out.
http://www.myphysio.ca/education_ballet.php