Advantage rolls

Story: As a GM or Player, I want to specify if a d20 roll I'm making is with "Advantage" (2d20 are rolled, but only counts the higher result), with "Disadvantage" (2d20 are rolled, but only counts the lower result), or "Normal" (1d20 is rolled, the result is the result). I need this so that I can play 5th edition D&D. Original: As a GM or player being able to select if rolls are advantage or disadvantage when rolling 2d20 to disable dice total and instead display high or low roll