D&D Character Builder
This is the official character builder. The demo only goes up to level three, but it has all the options from all the books in there.
If using premade modules then you should cover all four roles, but the game is designed to handle a missing role. And by the same token, people should hash out what race/class/build everyone is going to be. Rogues and Warlords both do better with more melee for example.