-This page by Voyd
Trox are a burly race of subterranean beetle-men that have the distinction of being the only 0HD race that's Large. They're best suited to martial roles, but it's possible to finagle them into other classes, including a few spellcasting classes.
Ability Scores: Trox get an absolutely monstrous +6 bonus to Strength, meaning that they're at their best in melee combat. Now what's the downside? A -2 to ALL of their mental scores, and their size also means they have a hidden -2 to Dexterity. However, the mental penalties can be offset by the Strength bonus, even for a few spellcasters.
Size: Trox are the only Large race, meaning that they have long natural reach, a bonus to their combat maneuvers, and an already-factored bonus to Strength. There are downsides, though: A trox is never going to be sneaky, and they also have a penalty to their AC, so they're a bit easier to hit than most characters.
Type: Trox are... well, it's inconsistent. The Bestiary entry says that they're monstrous humanoids, but the "monsters by type" list places them under humanoids. Better get your GM's opinion on this, though I'm pretty sure they're supposed to be the former. If that's the case, then they can't be enlarged, but since they're big fellows already, do you really need enlargement?
Frenzy: You get a pseudo-rage! It's only useable once per day, but here's how to rage as a lawful character.
Grabbing Appendages: Hey, it's a race built for wrestling! You get Improved Grapple, and the best part is that you can maintain a grapple and still attack other creatures. Very nice!
Alchemist: Even with an Intelligence penalty, a trox can make for a very nasty mutagen-based alchemist. ALL THE STRENGTH BONUSES!
Barbarian: It's obvious that this is the role that trox were meant to play, as the sample character in Bestiary 4 is a barbarian, and they also have a racial pseudo-rage anyway that stacks with rage. Multiclass into alchemist to snag a mutagen and you become a melee nuke.
Bard: Penalties to Intelligence, Dexterity and Charisma means that trox are never going to be good at performing.
Cavalier: I don't think the APG writers anticipated a Large race. What sort of gigantic mount would a trox use, anyway? An elephant? If anything, I'd house-rule that trox can't take the Mammoth Rider prestige class, since they'd need a Huge mount to support their weight anyway.
Cleric: Why are you playing a full spellcaster as a trox? If you want to cast spells, go with the alchemist.
Druid: I repeat. Why are you playing a full spellcaster as a trox?
Fighter: Melee is your best option here, and you can still make use of the Frenzy ability. You want a big stupid fighter? Here's the biggest and stupidest fighter around!
Gunslinger: Penalties to both Dexterity and Wisdom? Get in the fight, sissy. Still, the prospect of a musket that fires a 3d6-damage touch attack is super tempting...
Inquisitor: Just like with the Gunslinger, the trox inquisitor suffers from from penalties to both Dexterity and Wisdom. However, inquisitors can operate in melee, and the Black Powder inquisition means that you, too, can have a 3d6 touch attack musket!
Magus: This is probably the best arcane spellcasting option for the big bad beetle. He the only offensive spellcaster that can really benefit from Strength, and even the Intelligence penalty isn't that crippling, considering that you're probably going to HULK SMASH people with magic.
Monk: While the Dex and Wis penalties are at first off-putting, a trox can make a surprisingly good wrestler monk, considering their massive bonuses to damage and grappling.
Oracle: This is probably the only full spellcasting class I can recommend for the trox, and only because of the Battle mystery. Grab that revelation for weapons proficiency, and go to town with magic and mace. Even with the Charisma penalty, a battle oracle is a good option for the bug.
Paladin: I have a hard time imagining a trox paladin. They're typically chaotic neutral, and they're probably distrustful of any authority after their enslavement by the duergar. That said, the Charisma penalty isn't that much of a setback, since your Strength is going to give you a lot of base damage for smite anyway. Also, the Cha penalty doesn't affect spellcasting much, since paladins only go up to fourth-level spells.
Ranger: Ignore the Dex penalty, it's not an issue if you focus on melee. The Wisdom penalty does hurt your skills a bit, but a trox ranger actually isn't that terrible.
Rogue: This is a no-go. Rogue need Dex and pretty much all of their mental scores, and trox just don't have any of those. This is almost worse than the bard.
Sorcerer: Penalties to all three mental scores means even the Empyreal and Sage bloodlines won't help you here, though the Abyssal bloodline does grant a bonus to Strength. Regardless, this just is not a good choice.
Summoner: Why would you want a monstrous companion smaller than you? Stay away!
Witch and Wizard: Hurr durr I am stupid beetle. If you want a full spellcaster, go with the oracle. If you want an arcane spellcaster, play a magus or alchemist.