I think this is incorrect, honestly. You don't have to assign a role before designing a creature. I could go through the 3.5 MM right now and describe them via a "role" if I wanted to, and many would be one role, some would be two, some would be more.
THIS, I think is the crux of it!
I have no problem with descriptive roles (particularly if the words to describe them are somewhat evocative..."brute" I like; "controller" notsomuch).
But, if they're going to be descriptive rather than prescriptive, then monsters must (perhaps quite frequently) fall into:
more than one role.
If a monster is made to "be a striker"...that's highly prescriptive...it's there as a game piece; it does damage - that is its alpha and omega, its reason for being.
If a monster is an "ogre"...and it does a lot of damage and has a healthy amount of hit points, then we can describe it as "full striker, part brute" or somesuch. Or maybe we do it cereal box style...where the most plentiful ingredient is listed first (no percentages/quantifications necessary). "striker, brute."
This, I think, is a major point that people are missing when talking past one another. Being provided only A SINGLE role as an option is both descriptive, but also prescriptive and pigeonholing. If a monster is to be "fleshed out", then more than likely it can act as a brute, or controller, or even fall as a minion in some circumstances (e.g. fire mephits in the arctic?).
Going full bore with this mentality would then involve, in the description, talking about HOW it is a brute and HOW it is a striker. What differentiates these tactics? Why might it act one way versus another? Does it have abilities that lend toward one or the other: e.g. Defensive stance brute for protecting the young'uns, Power attack for slaying intruders with no young'uns around.
The thing is, if we look at monsters beyond single encounters, they WILL be able to have more than one role. They may excel at a single role (or two, or three), but they'll have elements of others. That's part of the fun of monsters. Goblins might attack en masse (strikers or brutes? I dunno). They might drop a landslide and shoot with arrows (archers or controllers?) They might be minions for a powerful leader. But these goblins can all use
the same stat block, and can
still be interesting, maybe even moreso, because players know what to expect of the monster's capabilities, but not what the monster will do with those capabilities.
Sometimes player knowledge of monsters is a GOOD thing. When surprises happen it's not because "oh it's a templated goblin (3e)" or "oh it's a goblin brute elite warlord (4e)." Nope. It's just a goblin. He's wearing plate and has a bunch of other goblins using polearms to protect him. FEAR HIM!
EDIT TO ADD: One more thing. It's ok for monsters to suck at something.
If the party is engaging a group of ogres, and they don't have "artillery ogres" or "ogres with the nimble template"...then the players capitalize on a known weakness of the species, their lack of dexterity/clumsiness. If "ogre" becomes so malleable that there is an inevitable "good archer group" of them, then we get more monster blandness, because the strengths of a given monster type are drowned out by the lack of weaknesses of that type and across the board with all monster types.