Easy Dice is an RPG dice rolling app featuring the following:

Variety of die types: D2 D4 D6 D8 D10 D10x10 D12 D20 D30
Choose which dice to roll together. For example a D4 with two D8.
Re-rolling of dice. Tap dice to select which ones will roll and which ones will stay.
Adding up: Sums all the die face values.
Die sets: keep die sets for later.
No special permissions required.