I checked this out once and found a way to determine the "exact amount" of Mello Roos for any particular house in Irvine.
In the tax detail of the Irvine property tax assessment:
A house <strong>without</strong> Mello Roos will have the following Tax Type (the left column) under "Special Assessment User Fees": BA, B3, C7, E0 AND N1.
A house <strong>with</strong> Mello Roos will have all the ones above PLUS something else (i.e. MY, R2, R6). Add those together and that's the Mello Roos for that house.