Originally Posted by skymaster
Jerome: With the door open and latch hook out in the locked position look under the hook on the plate and you will see a small slotted head screw, that screw will adjust the hook in and out. That takes the play out of the door, adjust the hook IN to tighten the door. Also check the strikeplate in the jamb that the hook latches onto, it may have to be adjusted higher for the hook to grab.
Like he said, but also, make sure that you are shutting the door ALL the way into the frame. It may be that the latch hook is not going into the 'catch'. Some of these doors are made so tight that it takes a bit of force to push the door all the way in far enough to engage(for hurricane and water reasons) As doors get older, they often lower as the rollers wear. Some doors have height adjustments, others, you can adjust the 'catch' as Skymaster stated. If the door still moves freely, I would not worry about the rollers, but just adjust the catch.