Added more property help docs

app/private/docs/property/roll.md

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+# Rolls
+
+Rolls are properties that store the result of a calculation to a variable name when applied by an [action](/docs/property/action). The variable name only exists for the duration of that particalar action.
+
+Rolls can be useful if you need to deal the same damage to multiple targets, or if damage needs to be rolled then halved by succeeding on a saving throw.
+
+---
+
+### Name
+
+Name of the roll. This will be shown in the log when the roll is applied.
+
+### Variable name
+
+The variable name to store the result of the roll for the duration of the action. Must start with a letter and be made up of only letters and numbers without spaces, symbols, or punctiation.
+
+### Roll
+
+A [computed field](/docs/computed-fields) that is computed when the roll is applied by an action.
+
+### Don't show in log
+
+If set, the roll will be applied and store its result in the variable name, but not be shown in the log.
+
+### Tags
+
+See [Tags](/docs/tags)