Romulans should strongly consider building up their survey ships to the maximum of six. Some players believe that doing so is of limited value, as the Romulans enter the war late, and cannot even begin surveying in the off-map area until Coalition Turn #13 or so (taking into account that the on-map provinces must be surveyed first). Also, the Romulans could not build a base off map [they can in F&E2KX], which limits their ability to move ships into and out of the off-map area. Thus, while they do benefit from survey, the total number of survey points and subsequent Economic Points is limited relative to returns by maximizing survey for empires that enter the war early.
     However, the Romulans will need all the Economic Points they can get as the war drags on, and the Romulans are in a unique position to maximize their survey capabilities relatively cheaply.
     While the Klingons and Lyrans must build heavy cruisers for eight Economic Points, and then spend five Economic Points to convert them to survey ships (a total of thirteen Economic Points), the Romulans can build survey ships for as cheap as five and a half, net, Economic Points. How? Easily, by taking three WEs crippled in battle, bringing them back to the capital, and using a major conversion to convert them to PEs. The cost is reduced by one Economic Point while converting them during repair, but you must add one and a half Economic Points for the repair, hence the total of five and a half Economic Points. Be mindful that you can only make one such conversion per year.
     So, to maximize Romulan survey capability, you will spend 5.5x3=16.5 Economic Points for three PEs, and nine Economic Points for three additional survey slots. Your total outlay is 25.5 Economic Points.
     What is your return? Others have done the math and published the benefits of survey. Using similar mathematical analysis, you will earn on average an additional 72 Economic Points above what you would have earned over the course of the game had you only used the original three survey ships. So, your return is not quite 3:1, and your net gain is 46.5 Economic Points. While it might not seem worth the initial outlay of 25.5 Economic Points at a time you need them early in the war, those 72 Economic Points will be coming mostly at times when you need them even more; i.e.,  when you are operating at 50% income due to exhaustion. So, plan ahead.
     This math assumes you started with four survey ships actually doing off-map survey on Turn #13 after surveying the on-map provinces on Turns #11 and #12, and then adding one survey ship per year for two years. That is just three survey ships that could also start off-map survey on Turn #13. This math also assumes effects of exhaustion, but ignores use of Prime Teams or high-risk survey.