I think you're underestimating the degree to which multiclassing and careful construction can enable a character to move into other roles.
To cite a couple well-known examples first. In the Living Greyhawk games I play, one of my friends has a barbarian 1/Cleric 14. The character is pretty much straightforward melee character. He has a reasonable armor class. He has decent hit points. In general when I'm playing my cleric in the party, he acts as a tank/DPS. If he needs to, he can drop a heal spell though and if he ends up as the party's cleric, he can do the standard buffing/healing. However, the best use of his actions is generally putting a hurt on things.
Likewise, I've DMed for or played with a couple druids who took nature's warrior levels (and maybe a barbarian level or two) and spend most of their time wild-shaped into a bear, eating the bad guys. When they do that, they're very effective at it.
That's not particular news. Ever since third edition started, melee clerics and druids have been the targets of the "they can do everything my fighter can do and more" complaints. (It's not quite true, but it's close enough).
My own first Living Greyhawk character was a fighter/wizard. By the time he made 18th level and retired, most of his levels were in Eldritch Knight, and he could fill in as the party's arcane caster in a pinch (in fact, he spent about half of his adventures as his party's primary arcane caster) but the way he would generally contribute would be through killing things with his sword, glaive, or later his guisarme. He might drop a quickened scorching ray before or after doing that. He might drop a wall of force in the surprise round instead of attacking, but he was primarily a melee character. (In 4th edition terms, he probably would be a controller/defender/hybrid who moved to more striker level damage in his higher levels).
To use a more exaggerated example, I have a friend whose mid level Living Greyhawk character is a barbarian druid who frequently wild shapes and charges. I've never seen the character summon an animal. If the party is relying on her for healing or support, they're in trouble. Unlike the other melee druids that I mentioned earlier, she is not a defender in 4th edition terms. She is pretty much a pure striker and plays like the most aggressive kind of barbarian (does a lot of damage and sucks up a lot of healing).
Another example of an unusual character is a friend's bard. Said bard has spent all his feats to be good at melee combat and is actually a pretty decent defender and can carve up the bad guys well enough even though everything in his class is focused towards the "leader" role. (And he does that as well as any other bard as well).
Likewise, a character as basic as a single classed fighter (not that you see many of them or that they are actually simple to build or play) can easily fill the defender (fullplate, shield, etc) or the striker (longbow, etc) role in a party.
It's hard for non-spellcasters to do more than dangle their feat in leader or controller roles, but in terms of filling in the defender and striker roles, 3e is pretty wide open.
Kishin said:
3E's 'role expansion' is mostly illusory. The build options are certainly hugely diverse, but they're still within a reasonable framework. Sure, you can move toward the edges of that framework, and even dangle your feet off the side into someone else's territory....But you'll never be as wholly effective at ti.
Example 1: Character in the campaign I currently DM: A Ranger with the wildshape Ranger variant rules, as well as the Feats instead of Spell progression. He's still a striker type character (Especially since the player built him using skill tricks from Complete Scroundrel, making him incredibly mobile.)
Example 2: A warlock using Eldritch Glaive. Character becomes a melee character, but lacks the resilience of a 'defender' due to HP and generally lower armor (until he discovers the magnificent hax of mithral breastplates). Character is forced to rely on other warlock powers for defense, most of which provide evasiveness. (Fell Flight, Spider Climb, etc.)
