Okay, several months ago, I posted that on a Federation side, and I said I will do taht for most reaces, well, here we go, and my next one will probably be Romulan.. heh
NoQ'Duj Class: I don't usually use it since BoPs are around, and they are actually quite weak and expensive compared to the price of a BoP and its superior capabilities. I only use of for scouting, nothing more.
B'rel Class: Now that's the heart of my strike force, but not defense, heh. Awesome for hit and run actions, and getting rid of pesky old Venture classes too. I could also use these as "advanced" form of attack fighters, also mentioned to me once (Venture classes).
K't'inga Class: Thanks to its high tritanium cost, I don't usually use these ships a lot either, but I would recommend you to have at least 3 per 16 ships (1 fleet that is. ) And its special weapons are also devastating.
K'Vort Class: Now that's what I call a tough little ship, heavy firepower, and shielding, despite its size, but quite expensive. This I send for support and defense in early games. And put weapaon autonomy at yellow when you are using this ship, in large numbers, its conventional and special weapons can hurt your enemies substantially
Qaw'Duj Class: I mainly use this ship to destroy small to medium stations, ranging from defense stations to shipyards, but don't use these against starbases, your fleet on Qaw'Duj Classes will perish exceptionally fast.
Sang' Class: I don't use this ship very often, because of its weak shields, but good for secondary defense ships.
Vor'cha Class: Now here's an awesome ship, and this is what I personally like: No torpedoes!! But with a disruptor bank which causes devastating damage. I use this ship to get destroy all types of ships, small or large, strong or weak, doesn't matter, its all the same to this ship!

Sometimes, I sneak up with a couple of Vor'cha's up to the enemy's base and destroy the majority of their mining freighters.
Vutpa' Class: I like this shp too, armed with pulsedisruptors, which causes devastating damage to small ships, and if you can construct these ships fast, you can withstand a lot of pesky assaults in early games, no need to worry from Rhein classes or a bunch of Saber classes. but try and not use these in later games, which you will find yourself causing almost no damage toa Valdor or a Sovereign.

Cho'naQ Class: Quite Frankly, I don't even construct these vessels, thanks to its high Tritanium costs, but an awesome torpedo cruiser, which means its good for defense when you send all your Negh'vars to the enemy base.
Negh'var Class: My ultimate defense ship, but when you are going for a final assault, send them al with you with your main fleet, which should by then be composed of the majority of Vorchas, BoPs and K'vorts in small numbers
BortaS Class: A torpedo only cruiser, I never use this since I favor 100% accuracy weapons.
Well, I will probably post the Romulan side in a couple of months when I have time
I hope you liked them, and Qa'Pla! I will now go an play some FO now..