I have found 7 proof nickels, 1 proof half, 1 mint set only dime, and 1 mint set only SBA dollar.
Since the total number of proof sets is basically the same for all denominations, I am guessing it is either the larger coins are more likely to be spent, i.e. half dollars/dollars, or its just that were less total made of those denominations so they appear more frequently in rolls (higher percentage). I think pennies are the hardest to find as I have searched a ton of pennies and never found a one.