Rockstar's Dan Houser has confirmed to IGN that Red Dead Redemption will include multiplayer modes, with stagecoach races and charging horses action aplenty.
There isn't more information yet about the multiplayer. There will be more information soon.
Free Roam is confirmed.
In Free Roam you can get into groups called "Posses" and ride around the whole world of red dead redemption. You can have up to 8 people in a posse. You can encounter other posse's while roaming the west. You get character models by winning challenges, and your weapons are already with you since there is a class system. There are still random encounters in free roam, but probaly dumbed down due to the stress of having 16 max players and the whole world opened. Other modes such as deathmatch, team death match, and a special version of Capture the flag are confirmed.