How do I know that an "Orthodox" theological work is officially Orthodox doctrine? Whenever I read theological works written by Roman Catholics I know that, as long as there is an "Imprimatur" from a legitimate Bishop, I can trust it to be official Catholic doctrine.

On the other hand, whenever I read contemporary Eastern Orthodox writings, I'm not 100% sure how to tell whether or not its trustworthy, or simply rogue theological opinion.

So far I've been clinging to anything recommended by St. Vladimir's Orthodox Seminary.
Official Orthodox doctrine is covered by Orthodox Dogmatics. The good book on it is Orthodox dogmatic theology by protopresbyter Michael Pomazansky. All except written in the book, could not be treated as a real Orthodox Doctrine, but only as intepretations.

There are no simply rogue theological opinion in Orthodoxy, except that is condamned as a heresy on Councils: ecumenical, or local. There are the opinions that can talk about some things in Orthodox Dogmatics, that inagree with the main course, but not declared as a heresy. They called as individual theologic opinion.

One yet is. St. Nilus of Sinai said (in my retell): "We have the Creed, and for laic people it is enough to trust just in it".