Nope, no way to do it. There's also no way to know when you've re-rolled if the same values come up. (For example, you make an attack and roll a 6 on the die. When you hit
Roll Again, if another 6 is rolled, you can't tell. Did you hit the button correctly? Did it not register? I've filed a bug report that there should be some kind of history within the roll window (it doesn't even need to be persistent) so that the user can tell. It should also make Nat20s and Nat1s obvious. If you feel the same, file a bug report. The more reports, the better the chance it gets fixed.
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