Advanced keyboard shortcuts are a new Roll20 feature for power users which provides a greatly extended set of keyboard shortcuts from the default. You can turn on advanced shortcuts under the My Settings tab, check the box next to "Enable advanced shortcuts?"

These advanced shortcuts are simple keystrokes, and for the most part do not use modifier keys such as Ctrl or Alt. Some of them are sequence shortcuts. For example the shortcut for the Shape Tool is "f r", which means pressing the "F" key followed immediately by the "R" key one after the other.