Orcs Must Die! 3

I'm not 100% certain as to when scramble mode unlocks but it will tell you on the main menu screen if you don't have it unlocked yet and what you need to unlock it.

Now how to reroll a debuff in scramble you will need to go to scramble and play your first map (sometimes you won't even need to play a map, just look for where it says either "Reroll available" or "Reroll unavailable). Afterwards you will be able to press and then select the debuff you want to reroll by pressing and then press again to reroll as long as it says it is available to do so.