Quote Originally Posted by oaty
Even if you do'nt destrpy there temples the culture difference will go away, where the problem can kick in is when the city grows you ca'nt upgrade it and there may be no way to bring up the happiness other than to destroy it and tech it up for better happiness
I want to correct this a bit:

You CAN upgrade a Shrine of Esus or a Sacred Cave of Abobna into their Roman counterpart when the town grows. Even the boni will change to the Roman ones.

In fact you cannot continue building the foreign temple type, you will replace it by the next level above it of your factions religion.