If they should get the idea to breed, the third wheel in your trio will take quite a beating. At best they'll let the third Ram hang out near the top of tank, as far away from the nest as possible. However, not all Rams will breed these days, or even have the idea in their heads. Too much inbreeding in many of the lines. So, three may work.
What I would do is to find a shop that has a fairly large bunch of Rams and look for a pair in the dealer's tank that has already bonded. You may be able to pick these out if they seem to be defending an area of the tank, are nicely colored, and seem to be the two dominant fish in the tank. You'll likely end up watching this tank for a good half hour.. but most of the shops in my area dont mind customer's taking their time. (You could always ask the shop people if they could help ya!) Its a bit of a tossup, but if you really have to guess, go with the two most brightly colored and best looking fish in the tank. Often enough this will work out to be the dominant male and female in the group, and they'll eventually pair up, or at least put up with one another.
But that's just what I'd do..
>Sarah