Some roles, like defender, may not work as well without using a combat grid / miniatures - that's a real thing to think about as that becomes optional.
- Enemies suffer a -2 penalty to hit allies adjacent to you. This penalty increases by 1 at levels 5,10,15 and 20.
Hold The Line
- Once per round, when an enemy tries to pass within 25 ft. of you, you can Shift in front of them as an Immediate Action.
- Once per encounter when an adjacent enemy makes an attack that does not include you as a target, you can make a Basic Melee Attack against that enemy as an Immediate Action. This attack takes place before the target's attack is resolved, and deals an additional 1[W] damage. At 10th level, this attack deals an additional 2[W] damage, and at 15th Level it deals an additional 3[W] damage.
On the subject of roles, I can take them or leave them. I like that in 4E there is something to the Fighter other than being "sword-swing-y nonmagic guy", but I don't think that they're essential.
I could see a system wherein players can take options that make classes perform different roles, such as a Paladin taking options that make them a striker, leader, defender OR controller.
Or a Wizard for instance: