Sooo, like Powering down my Wii u, then Rerolling it again?
It works like this:
1. Copy your save to a USB drive.
2. Start the game with the USB drive inserted. The game will use the save on the USB drive, not the one on the system.
3. Reroll a piece of gear as many times as you want.
4. If you don't get what you want, return to step 1. This will give you your snails/coins back, so you can try again.
Once you get what you want, copy the save from the USB drive to the system drive.
You can do something similar with purchases from Spyke. The unlockable abilities are not determined until you buy the gear, so you can save before buying the gear, then keep buying it and unlocking the next ability until you get what you want.