That isn't how Evasion works
The Rogue Evasion feature allows two things:
- Against Area-of-Effect spells that trigger Dexterity Saving Throws, if the Rogue fails the Saving Throw, they take half-damage (instead of taking full-damage)
- Against those same spells, if the Rogue succeeds on the saving throw, they take no-damage (instead of half-damage)
It's possible you're thinking of the Uncanny Dodge feature, which a Rogue may use to cut incoming damage in half, using their Reaction, whenever they are hit by an attack.
These are two different features that both make up for the Rogue's lack of survivability, but have different mechanics and interactions: one (Evasion, at level 7) for spells, and one (Uncanny Dodge, at Level 5) for regular attacks.
The Uncanny Dodge feature should not be confused with the Dodge Action, which is an action that a Rogue (or any other character) may take during their turn instead of taking any other Action that confers Disadvantage on enemy attacks against them.