Rosewar was a role playing game, a postal simulation of the Wars of the Roses. I didn't get involved until quite late on, but for the last few turns I was the Earl of Warwick! It was tremendous fun while it lasted, but Steve, the chap who ran it, found the burden too much in the face of his growing family responsibilities, and it came to an end in 2004, just as we were getting ready to have a Parliament.
You may enjoy reading the archives and seeing the alternate version of history.
Those of you who would like to try something similar may enjoy the board game Kingmaker though to get the best results you really need a group of like-minded people who are willing to play for several days. An evening is not long enough. There's also a computer version out there which is probably to be found as a download nowadays - the graphics are ancient though, don't expect anything fancy.