How to roll dice with advantage or disadvantage?

The advantage/disadvantage mechanic allows you to roll 2 dice and keep the better one (for an advantage) or the worse one (for a disadvantage). It is widely used in the systems based on the 5th edition of Dungeons & Dragons.

The mechanics are built into the system

On Let's Role, advantages and disadvantages are included in many game systems that use this mechanic. For example, in the official Dungeons & Dragons system, it is possible to choose to Roll normally, Roll with Advantage or Roll with Disadvantage via the drop-down menu under the character's avatar.

Note that the presence, wording and location of this mechanic depends on the system used.

The mechanic is not integrated in the system

If the mechanics are not available in the system, it is possible to use the functions keeph for an advantage and keepl for a disadvantage. These functions can be used directly in the chat (e.g. /r keeph(2d20) +2) or in custom shortcuts in the QuickBar (e.g. keepl(2d20)+2 in the Dice formula box).

keeph and keepl mean respectively keep higher and keep lower.