Quick Question About Emboldening Bond

[ATHATH]

When, exactly, do you choose whether or not to add the d4 from it? Can you roll a d20, see the number on the die, and then choose to add a d4 to it if it looks mediocre, or do you have to apply the d4 before rolling? Can this be after your DM declares whether or not an attack or save succeeds/fails?

[stoutstien]

General rule if it's not stated you see the roll but must decide to add it or not before the outcome is determined.