The thing you might be looking for is the Law of large numbers. The theorem states that the average of the results obtained from a large number of trials should be close to the expected value and tends to become closer to the expected value as more trials are performed.

So if you roll the dice 1000 times, it is astronomically unlikely to never roll a 6, or that all 1000 will be 6s. It isn't impossible, but very unlikely. The distribution of how many times a number was rolled should approach 1/6 for each number.