You can have many temples in a region. One to as many religions as you wish.
Of course, only the region lord can build a temple, anyone can loot them, a region lord can close the, and other fun stuff.
And the region lord must be a member of the religion in question before he or she can build a temple to that region.
Let us say that very few regions have more than one temple, and fewer still have more than two temples. I cannot in fact think of one that does.
