Those interested in signing up for the beta program can do so here. The entry form notes that by referring five friends to the program, you are guaranteed access to the beta version of the game.
Medieval Multiplayer Accepting Applications for Early Access
NEW YORK – July 6, 2012 – Paradox Interactive and Fatshark announced that, after recently completing a successful closed alpha, sign-ups for a chance to participate in beta testing for upcoming medieval multiplayer combat title War of the Roses has now opened to the public. Starting today, players can enroll to be a Knight in the King's army and help restore order to England by visiting the following link: http://www.waroftherosesthegame.com/
When signing up to guarantee their access to enter the beta, future knights will obtain a unique referrer URL from the King that can be shared across social media channels. When five friends use this player-specific link to sign up for the beta, the player who is linked to the URL will be granted a secure spot in the beta.