Is the goal to get rid of roles, or to make all roles available to everyone?
If the goal is to get rid of roles, well, I'm not sure what you should do because no matter what rules you set your players will choose to specialize. In my experience, "no roles" usually means "everyone is a striker."
If the goal is to make all roles available to everyone, the first thing you should ask is if there's some actual concept that one of your players wants to use that isn't presently available. If there isn't one, don't mess with things. If there is, ask yourself why its not available, and what the minimal intervention necessary to make it available would be.
If, for example, the issue is that you have a player who wants to play an archer but doesn't want to be woodsy like a Ranger, would he be happy using the Ranger class and just altering the mandatory Nature or Dungeoneering skill to some other knowledge skill?
Or if the problem is that someone wants to play a Rogue who wields a Greatsword, figure out what it is that says "Rogue" to him, and see if its obtainable through some other class combination. For example, a fighter who uses heavy blades gets a lot of benefits from a high dexterity, there's no armor check penalty in scale armor, and it only takes one feat to train a character in Thievery or Stealth. Would he be happy with a strong, agile fighter with a greatsword who can hide and pick pockets? Or is the objection more mechanical- that he wants to stack sneak attack and a greatsword's damage dice together? If its the latter, should you let him do it?
Anyways, consider why you're considering a change, exactly. And then consider whether some smaller change wouldn't accomplish the same thing and get you back to the game table as quickly as possible.