Square dancing is not an individual sport, it's a team sport. It means being at the right spot yourself, making eye contact, and touching hands. It also means that the people who have the easy parts of calls watch out for those who are doing the hard parts. Not only should she not wander, she should be watching for that center to show up, and extend her hand to make clear which of the three dancers on that side of the square wants to cast with him. Move in time to the music.
Some people have a tendency to hurry up and wait.
That ruins the flow of the dance, making it less pleasant. You can almost always move in a smooth continuous movement. The proper dance step is closest to walking, not prancing. Moving with smoothness will help keep the square together. Being cognizant of flow, or at least not resisting it, should also make the call ROLL easier.