I'm not too sure what you're trying to achieve here... Usually a monitor will have BNC connectors for RGB inputs, not RCA..
Anyway, in the case that it does have RCA, its simply a case of wiring R, G, B and Sync to individual connectors and then splitting the ground 4 ways onto the outside of each of those.
I know it has BNC. I've used some BNC to RCA adaptors on the monitors BNC outs to make life a little easier.
Sounds like it should be pretty easy, another question. Does the saturn RGB SCART have all 10 pins wired to it?