In hospitals, the nurse schedules are sensitive to disruptions such as sick leave since the absence of nurses with the right skills can have a severe impact on healthcare quality. We consider nurse rerostering from a strategic perspective in the case of having multiple skills and varying staffing demand. Our aim is to design a decision support tool to be used on a strategic level to analyse how the distribution of skills affects the sick-leave robustness of schedules. Schedules are evaluated based on generated scenarios with sick leave and possible rerostering of tasks. We have performed a case study at a ward in a Swedish hospital, and show how our tool can be used to indicate which of the available skills can be removed, with only a small impact on the understaffing in the nominal scenario and in scenarios with sick leave.