My apologies for a long post, but I've thought about this kind of a lot, so I hope it's worth it.
Three of the four roles have existed in every edition of D&D(and for that matter, most RPG systems):
Not the same roles. Not by a long shot. Most earlier editions had what you might call "dungeon exploration roles." Combat was an assumed risk, but so were traps and magical teleportation chambers, and you had three people to deal with these risks: one to bop goblins, one to disarm traps, one to basically solve magical puzzles, and one to put the other three back together again when they didn't do so hot.
It might help if I summarize what I said back in that noncombat roles thread, for context, so that's in the spoiler block.
[sblock=the true roles]
Take a step back and look at how combat in any edition of D&D actually behaves, why it's interesting, and why it generates tension.
The basic thrust of it is that you have two sides with a pool of points. Each side can take the others' points. The first team to 0 looses.
This is the basic game of D&D combat in any edition.
This basically implies two main roles: Attack (take points from the other side) and Defend (stop points from being taken from your side).
This can be made more robust, because there are kind of sub-roles for it:
Attack 1: Take points from the other side ("direct damage;" probably closest to the 4e striker).
Attack 2: Make it easier to take points from the other side (including buffing your side's damage, and de-buffing the enemy's defenses; 4e's Leader class does the former, but there's no specialist in 4e for the latter, it's spread out amongst all the classes with "conditions")
Defend 1: Give your side more points ("healer;" basically the main purpose of 4e's Leader role, though a bit of healing has been given to every character in the form of the second wind)
Defend 2: Make it harder to take points from your side (including buffing your side's damage resistance, and de-buffing the enemy's attacks; 4e spreads most of this out with conditions, and especially with movement, which is 4e's #1 buff and de-buff method).
The sub-roles don't really need to be divorced from the major roles; it kind of depends on how much granularity you want in your rules.
[/sblock]
So, any time there is a "first one to 0 looses" kind of system, there are at least two roles (and there can be a lot more if you want to get super-specific about what each role does, and for the important stuff in your game you do want to get pretty specific, because it's more interesting and strategic then).
Given that...
1. Defender=Tank--Aside from the minis skirmish aspects you describe, the Defenders role is to engage the enemy. The job of engaging the enemy does not require the miniatures skirmish stuff. Engaging the enemy is accomplished by being able to survive being engaged back while being dangerous enough that disengaging from you is a less attractive choice than beating you down. The monsters themselves mean to engage the PCs, preferably the squishy ones first, and what you accomplish as a Defender is making sure things go your way. This role exists independantly of the skirmish aspect of 4E, and the main difference 4E adds is that it is the first edition of D&D to truly give the Defender the tools to do this right.
The "stop the bad guys from taking my points away" role is in any "first one to 0 looses" system, and so it's in every edition of D&D combat. The icon of this role is usually the fighter. In earlier editions, the fighter was the only reliable combatant. Usually, they went in the front lines. Frequently, at early levels, they represented the greatest threat to the enemy. At later levels, they were often eclipsed by a Wizard, but even then they could last long after the wizard became useless (which, in earlier editions, was rather more frequent, as "gotcha" abilities were common, especially for spellcasters).
The fighter was always the most secure pool of points in the party. As long as the fighter lived (which it was the best at doing) the party could never die (resurrection, etc).
Where 4e's Defender takes a slightly different track, it is in encouraging enemies to target them. This improves their ability to keep points from slipping away.
However, 4e's Defenders can't do this from just anywhere. They need to be in fairly close range with the enemy (minis), and once they are there, the enemy can't get away easily (minis). The main method of avoiding this fate is by moving (minis).
Every edition's fighter managed to keep a pool of points from slipping away in combat. Only 4e's Defenders use battlefield positioning heavily to do so.
2. Leader=Healer--Its the Leader's job to keep everybody alive. This is the easiest one to understand, as you've stated.
Check out how often the Warlord moves little pieces of plastic around the board. Push, pull, shift, slide...these words are all most relevant to minis combat and not very relevant outside of it.
The 4e cleric doesn't do it very often, though.
And it's true that the "leader" role is the role that is closest to one of the actual roles: giving points back to your team is one of the most effective ways of making sure the enemy gets to 0 before you do.
3. Controller=Raw Power--Even detached from 4E's take on it, the Controller role has always been about applying as much brute force to the situation at hand as is possible, either through control or blasting. 3E's Wizard, while able to do a lot of what the Striker of 4E does and can even play games to summon Defenders and buff the party like crazy with things like Haste, was always at his/her best when asserting control, and it was a unique ability that nobody did better. Even good old AD&D Fireball spamming Wizards were Controllers first, though more often of the blasting variety.
Here you're starting to get part of that dissonance between the actual roles and 4e's stated roles.
In earlier editions, wizards actually were very binary in combat. Either they had nothing (I've used my Magic Missile, and now I basically run away) or they had it all (Sleep...battle's over). They would either make all the points go away in extreme attack vein, or they would basically only exist as easy targets, without real defenses.
What minis combat focuses on is positioning, movement, little fiddly bits of relative space. Controllers are in love with minis combat. Heck, the entire reason controllers *exist* is minis combat. Yes, every wizard could make a wall in earlier editions, too, but the wizard's JOB was generally to kill things and then get the hell out of the way (in the same way that the fighter's job was "don't die").
The 4e roles are not the same roles that these things always had. They share some similarities, but even leaders are defined, in 4e, by much more than "I heal hp" (which was pretty much what the cleric of earlier editions was defined by). Fighters were never very "sticky." Paladins didn't hurt you for ignoring them. Wizards weren't masters of zones. Thieves weren't just there to backstab. Those extra qualities are mostly about minis skirmish, about motion. It's important for 4e to have these, because the minis skirmish is at the heart of the game, but it's never been (and never will be) at the heart of MY games.
Indeed, in earlier editions, the "roles" were balanced out, in theory, by being about more than just combat. They were all ways to get to the end of a dungeon: fight (fighter), sneak (thief), or cheat (wizard), and one way to help you out when something went wrong with one of those plans (cleric). Thieves weren't supposed to fight, and Wizards were generally only supposed to fight things they could easily kill, and clerics were only supposed to fight enough to be able to heal up the others who were fighting.
The roles aren't exactly brand new, but they certainly aren't the same thing with a new coat of paint, either. They're as much about motion as they are about the points for each team, and in that way they are about
minis (in a lot of ways, minis = motion)
They aren't. 4E uses a minis/skirmish style, and the roles define themselves within those terms, but the roles exist outside of minis/skirmish. Defenders engage, Leaders heal and buff, Controllers dominate, and Strikers hit hard and run away. Minis and skirmish rules are not necessary for any of that.
How do you tell if something is a Defender in 4e? In part, if it can stop things from moving (minis).
How do you tell if something is a Controller in 4e? In part, it moves around the enemy (minis)
How do you tell if something is a Striker in 4e? In part, if it has a high rate of movement (minis).
How do you tell if something is a Leader in 4e? In part, if it moves around your allies (minis).
What was a fighter known for in earlier editions? In part, having a high AC (points).
What was a wizard known for in earlier editions? In part, "instant death" spells and buckets of d6's (points). Also flight and teleportation and invisibility (exploration)
What was a thief known for in earlier editions? In part, the ability to climb walls, hide in shadows, and disarm traps (dungeon exploration). Also backstab (points).
What was a cleric known for in earlier editions? In part, the ability to heal hit points and increase the party's defenses (points). Also divination (exploration).
A cleric is not a leader. A fighter is not a defender. A wizard is not a controller. A thief is not a striker. The 4e roles are similar (combat is still a "first to 0 looses" system after all), but have adopted qualities intrinsic to minis combat (movement).
I think we pretty much see eye-to-eye on the other stuff.
