The only thing someone needs to do to prove that false is to demonstrate that they personally had these roles before 4e. I'm taking a lot of 4e fans at their word when they say that they had these roles before 4e, but there's no reason to doubt that. A supporting argument would be along the lines of "The simplest reason for WotC choosing those roles was that these are the roles they identified people playing with." Thus, it must be true that D&D as a game had these roles. If some folks played with 'em, the game as a whole had 'em.
We need to make a distinction, it seems.
On the one side, we have the game as it was played. As it was played D&D had these roles before 4e defined them.
On the other, we have the game rules as they are written. As they were written D&D had no roles before 4e defined them.
When someone says "4e only defined the roles that have always existed," they are talking about the game as it was played, pretty clearly (they're not typically asserting that D&D had defined these roles in hard rules somewhere -- that'd be demonstrably pretty false). When someone says "4e invented the roles whole cloth!" they're ignoring the game as it was actually played -- they're asserting that unless it's written as an offical rule, it didn't exist. Which is a little like claiming that XP awards based on story pacing don't exist before they were written about in a DMG -- clearly, the practice isn't dependent on a formal rule.
Yeah, there's a lot of diversity. But I presume that 4e's designers did some homework, and I presume that 4e fans who speak of roles like this aren't lying. Those aren't very big leaps to make.
It'd be fair to say that it existed as an attack roll throughout all editions for some tables, and for others, that it was new to them in this edition. For the game as a whole, then, it has existed throughout all editions. Those who have always used it are still under the umbrella of "playing a D&D game."