Not having the book myself, could you reasonably summarize what the monster's behavior is? Usually a role will tell you how a particular monster performs. Maybe as a solo, this guy does things in a very different manner?
I'm going to post his stats, although, in order to avoid running afoul of copyright, it will be severely abridged and incomplete with regards to combat-irrelevant details.
[sblock=Level 33 Solo Primordial from the Forgotten Realms Campaign Guide]
Blazing Rorn the Fury, Level 33 Solo Primordial
Huge elemental humanoid (earth, fire)
Blazing Aura (Fire) aura 10; creatures in the aura lose fire resistance. Each creature that starts its turn in the aura is pulled 2 squares. When Rorn is bloodied, each creature starting its turn in the aura also takes 20 fire damage.
HP 1545;
Bloodied 772; see
fury of blazing stars
AC 50;
Fortitude 51,
Reflex 45,
Will 48; see
volcanic retort
Immune attacks by characters below level 20; fire
Saving Throws +5; whenever an attack applies an effect to Rorn that a save can end, he makes an immediate saving throw. If it succeeds, he is unaffected by the effect. Rorn makes saves at the end of his turn as normal.
Speed 10, climb 10; earth walk; phasing through earth or lava
Action Points 2
Claw (Standard, At-Will)
Reach 3, +38 vs AC. 3d8+12 damage; ongoing 5 fire damage (save ends) while Rorn is bloodied.
Tail Smash (Minor, At-Will)
Reach 4, +36 vs Reflex. 2d10+12 damage, and the target is knocked prone; ongoing 5 fire damage (save ends) while Rorn is bloodied.
Earth Chains (Minor, recharge

)
Ranged sight; +36 vs Fortitude or Reflex. 2d6+13 damage, and target is pulled 10. Flying creatures hit by this are slowed (save ends); ongoing 5 fire damage (save ends both) while Rorn is bloodied. Failed save: Target can't fly, and falls if it's airborne (save ends).
Dominion of Flames (Standard, recharge

) *
Fire
Close burst 20; +36 vs Reflex. 2d8+13 fire damage and ongoing 10 fire damage (save ends).
Volcanic Retort (Immediate Reaction when hit by an attack, At-Will) *
Fire
Close burst 2 (burst 5 while Rorn is bloodied); +36 vs Reflex. 2d8+13 fire damage.
Threatening Reach
While bloodied, Rorn can make opportunity attacks against all creatures within his reach (3 squares).
Fury of Burning Stars (when first bloodied, encounter)
Rorn changes to his "blazing star" form; his size increases to Gargantuan. He takes an extra turn right after then turn of the creature who bloodied him, then resumes his normal place in the initiative order. He remains in blazing star form for until the end of the encounter.
-------------------------------------------------------------------------
Tactics:
Begins with
earth chains, pulling enemies into his
blazing aura and melee attack range; repeat every round, when necessary. He blasts nearby enemies with
dominion of flames while they have no resistance, then uses another minor action to
tail smash. He continues with
claw and
tail smash attacks, plus
dominion of flames when available, until bloodied. Once in blazing star form, he uses his extra turn to destroy a badly damaged enemy.
Notes:
- There's several mentions to something called "blazing action", but I don't see it anywhere.
- In the stat block, the bloodied line references something called "volcanic reaction"; presumably, volcanic retort was meant.
- "Immune: attacks by characters below level 20"; wow, cool! Although, they shouldn't be fighting this guy anyway.

- Tactics seem to suggest that Rorn doesn't mind taking on whole groups of enemies simultaneously.
[/sblock]There he is; you can tell me what his role is, now. (There's about three and a half more pages of details about this guy and his servants in the FRCG; he'd make a cool superboss in any campaign, so if you really like this monster, I suggest you buy the book.)
(Note: If this statblock is a problem, I will remove it on request. I tried to paraphrase as much as possible and leave out details that weren't directly relevant to the discussion, so as not to infringe upon any IP rights. However, if this isn't good enough, so be it.)