Suggestion for Slots

Roll four dice

Bust if no dice match each other -- 27.78%
e.g. 1634, 6342, 5124 etc.

Normal if exactly 2 dice match ---- 55.56%
e.g. 1531, 3431, 5366 etc.

Jackpot if 4, 3, or two pair ------ 16.67%
e.g. 1111, 4244, 3223 etc.

Impact of a single reroll:
No point rerolling unless two or none match.
If none match, irrelevant which is rerolled, and can change to match one not rerolled
--> P(bust -> normal) = 1/2

If two match, can change to create either 3 or two pair
--> P(normal -> jackpot) = 1/3

Therefore
P(bust) = 27.78% with no reroll, 13.89% with one reroll
P(norm) = 55.56% with no reroll, 50.93% with one reroll
P(jack) = 16.67% with no reroll, 35.19% with one reroll

cba to work out two rerolls because the outcomes get hella entangled, especially with the fact that you aren't allowed to reroll the same die twice, so it matters which one was rerolled the first time. Also why would you waste two rerolls on one Slots attempt, really.