Depending on what your objective is, you might not need to enlarge the default Rollup icon.
If you just want to make the rollup status more visible, instead of enlarging the default rollup icon, you could use the build-in shape function, draw a shape, with any size you like, in place of Rollup icon.
See the following screenshot, where an ellipse shape is drawn to represent the rollup status, and check out the size.