The system is "Marvel Heroic RPG" by Margaret Weis. Basically you build a dice pool that can consist of multiple dice between D4 and D20, you roll them, then make a total number of 2 of them, and use one as the "Effect Die"
So for example:
I roll 2D8, 1D4, 1D12 and 1D20. The results are as follows:
D8's roll a 2 and a 5
D4 rolls a 4
D12 rolls a 6
And the D20 rolls a 13
Seeing those rolls I can decide to use the 8 that rolled a 5, The D20 that rolled a 13 for a total of 18, and call the D12 my effect dice. It works in the system to get a number and a difficulty class (The Effect Dice).
The display would basically have to show each die, and what they rolled. Even duplicate dice should be listed seperately either individually or as above "D8's rolled a 2, 5" would work, as long as it showed what each individual die value rolled.
I hope that isn't too confusing!