Not all rollers fit in the bins. The names say something about the width of the roller surface. For example, the Bucket 18 is suitable for rollers with a width up to and including 18 cm. The Bucket 25 is suitable for rollers with a width up to 25 cm.
A slightly wider roller may still fit, but will no longer be able to roll over the entire rolling surface because the rolling surface will then become too narrow at the top.
For storing rollers in the paint, we have made the lid extra high. Most rollers fit into the bins including the handle, when the roller is placed on the bottom of the bin. If the handle is too high anyway, remove the roller from the bracket and place only the roller in the bin.