5E - Turn Based Effects

[Roach]

You might be able to set up s.th. like that using 'Untrue Effects' and use an analogous setp to Warlock Hex effects...
Ger an effect on the target that expires at the end of the round and check for (absence of) that ffect on a hit.

[MrDDT]

You can use untrue effects couple with BCEG.

Use the effect that adds an effect when you do damage. This will track when you hit a target. This effect have it fall off once the turn changes. Then use untrue effects to detect to see before each attack if it has that effect.