You can simulate dice (with any number of sides) using the random() expression.
From Construct 2 Manual:
"Random(N) - Returns a random number between 0 and N, not including N. The result includes fractions, so random(3) can return 2.5. Use floor(random(n)) to generate a random whole number up to but not including N, e.g. floor(random(3))* will return either 0, 1 or 2. Random(A, B) can also be used to generate a random number between A and B."
To simulate 6 sided dice use: floor(random(6)) + 1
If you need the sum of dice values, I'd suggest you make a function like the one below:
When you call the function you say how many dice you need to roll and it will roll all dice and return the sum.
eg. roll(3) to roll 3 dice and get the sum of the results or roll(1000000) to roll one million dice and get the sum of the results.
Hope this helps. Cheers!