Rose diagrams are useful in fieldwork to analyse data containing magnitude and direction values. For example, they are commonly used to display the direction, strength and frequency of wind or ocean waves. Rose diagrams can also be used to represent data that has cyclic characteristics, such as yearly or daily variation.

Florence Nightingale invented rose diagrams to show how many more English soldiers were dying of cholera and other preventable diseases (blue) than battle wounds (pink) during the Crimean War. (Black is all other causes of death.) Each wedge represents a month. The rose chart on the right is before sanitation measures were implemented, and the chart on the left is after.

Source: Florence Nightingale understood the power of visualizing science

Another example of a rose diagram is this: the nine planetary boundaries, showing estimates of how the different control variables for seven planetary boundaries have changed from 1950 to present. The green shaded polygon represents the safe operating space.  Source

One final example comes from an academic paper which sought to assess the impact on health of different sources of pollution in a region of Iran. The rose diagram shows the wind direction and speed on different days. Source