Part 1: The roles in D&D (defender, leader, striker, controller) and WoW (tank, healer, DPS, and a side order of crowd control) aren't inherent in player psychology.
Part 2: You can't find proto-roles in the fantasy literature that inspired D&D (and thus WoW) or in other relevant cultural touchstones like comic books or Star Wars.
Part 3: Tanks emerged in D&D because magic users could not survive low level gameplay, and in a cooperative game like D&D, everyone contributes to keeping that guy at your table happy.
Part 4: Healers emerged because magical healing was so important to keeping a D&D party active and engaged in the ongoing narrative, but that magical healing was available from only a handful of the original character classes (the cleric, mostly).
Second, some disclaimers:
• I wouldn't dream of arguing against the notion of roles in any game that involves small-group cooperative efforts. When I say, "there's nothing inevitable about the roles we got," that's very different than the (probably bogus) assertion that "there's nothing inevitable about roles."
• Other games are going to have other roles. A lot of the skillcentric tabletop RPGs of the 1990s had specific roles for the skills (flying a starship, computer hacking, etc.) that were crucial to the setting. The tabletop wargames I'm fond of certainly have broad "roles" you could assign to each of those cardboard chits. I'm mostly interested in roles in D&D and WoW because a) I've played them a lot; and b) they cast an awfully long shadow in their respective game genres.
OK, So Let's Talk Alternatives
If the roles we wound up with trace their origin to specific design decisions Gary Gygax made in the 1970s, then...can we do other things? (Assume a fantasy context here for the tabletop RPG or MMO in your head.)
Sure you can--but realize that you're heading to the deep end of the design pool. That basic tank-healer-DPS trilogy controls your overall pacing, it largely determines what the monsters are doing at a given point in time...it goes on and on. Those roles touch almost all the other mechanical elements of the game. The flavor of your classes (or however you define a discrete batch of character abilities) is rooted in those roles.
But you know what? If Gygax did it, you can too. My buddy Toby and I came up with the skeleton of a pretty good alternative over a lunch at a brewery a few weeks ago. (Someone might pay me for it, or I'd just lay it out here and now.) Look at how humble the roots are for tank-healer-DPS.
But Should You Come Up With Alternative Roles?
That, I think, is the real question. The role setup we've got is a double-edged sword--and I mean that in the truest sense of the word.
Say you're designing a new MMO intended for a niche within the existing MMO audience. Should you build your game with tanks, healers, and DPS?
Yes. You want people to grok your game quickly, and if new players can slide into roles they're already experienced with, they'll thrash around less during those critical first few hours. And those roles are a ready-made tool for assembling small groups of strangers. Converting thousands of strangers into a cohesive community is really what the first weeks and months of an MMO is all about. It's a readymade social convention that most people already know--even if they don't know anything else about your crazy new MMO.
No. The roles we've got are looking a little shopworn, and there's not infinite design space inside the tank-healer-DPS triangle. Especially outside the swords-and-sorcery genre, the roles don't speak to the source material.
A lot of MMOs (and tabletop RPGs for that matter) are going to launch in the next couple of years, many of them outside the fantasy genre. Here's what I hope: Those games that have crazy-mad innovations that are pervasive throughout the game--you guys stick to the roles we've got, just to provide a solid vantage point for us to see all those crazy-mad innovations you made.
The rest of 'em: Come up with new roles! Don't make me be a superhero healer or a "tank" for the rest of my infantry squad. (I'm willing to be a literal tank, however.) Make me something that's organic to the game I'm actually playing, not just something I've been for decades. Every time you force me into the same role structure without a damn good reason, I'm gonna shed a tear like the Indian who finds trash on the roadside.
And when you're playing a new game: Don't let us designers off the hook on the whole "role" thing! Demand roles that make sense mechanically and stay true to the source material.
Out of Context: Shugo Nom Nom Specialist--too silly?
Music: Fugazi, 13 Songs