Classes

Exceptions will be on a case-by-case basis. The purpose is to focus on the culture, not to force you to play characters you don’t want to play.

MARTIAL

Covers most nobles, commoners, and outsiders alike
Assassin (Executioner) (S): Even more focused on sneaky killing than a rogue, which means very Scorpion-esque, although the Hiruma scouts might welcome such skills
Barbarian (Berserker) (D/S): A good way to show a conflict or balance between honorable behavior and letting loose (as exemplified by Hida Kuon)
Fighter (Knight) (D): Relies primarily on shields, so should not exist
Fighter (Slayer) (S): The perfect representative of the two-handed sword (or axe or hammer, for our Crab friends) warrior
Fighter (Weaponmaster) (D): Good for a two-handed or dual-wielding sort who still wants to defend his liege and comrades
Ranger (Hunter) ©: Archery is practiced by samurai, although not usually as a primary focus except by the Mantis Tsuruchi family. All rangers will likely use martial utility powers typified in the Player’s Handbook and Martial Power, not the more overt primal magic of Heroes of the Forgotten Kingdoms.
Ranger (PH) (S): The focus on single-target killing could show some connection back to the courtly roots.
Ranger (Scout) (S): Wilderness warriors are generally more common among Crab and Unicorn than other nobility.
Rogue (Scoundrel) (S): The Charisma build is a good fit for those who focus on politics rather than combat or magic, although this is not popular among the Crab. The proficiency with throwing stars also fits the setting, showing how people could have come to hear myths about ninja.
Rogue (Thief) (S): The focus on sneak attacks is a very un-samurai style that is more common with the Scorpion and certain minor clans.
Warlord (Marshal) (L): Popular everywhere

ARCANE
This allows people to dabble in both elemental and shadow magic, and thus is a good representation of both shugenja and blood sorcerers, who draw on power from the various Spirit Realms.
Artificer (L): This could be good for those shugenja who focus on craftsmanship, such as the Asahina of the Crane or even Kaiu who show spiritual talent.
Bard (PH) (L): Or a shugenja could focus on social skills, regardless of whether or not that includes musical talent.
Bard (Skald) (L), Swordmage (D), Wizard (Bladesinger) ©: This is an iconoclastic mixing of the two expected roles for members of the samurai caste, which could result in no one accepting you outside the Crab.
Sorcerer (Elementalist) (S), Wizard (Sha’ir) ©: A little more elemental focus in the form of resistances and either particular powers or an exclusive familiar
Warlock (PH) (S), Wizard (Witch) ©: Different (or multiple) pacts/patrons could show focus on different spirits, like elementals or ancestors.
Wizard (Arcanist) ©: The options for tomes are a good representation of the traditional bundles of prayer scrolls, including a possible focus on summoning elemental (or shadow) spirits.

PRIMAL/PSIONIC/SHADOW
This mostly comes into play to represent those who use subtle magics to be more awesome in martial-looking ways, similar to physical adepts in Shadowrun. The more flagrant uses (as by shamans and psions) are not known in Rokugan.
Ardent (L), Battlemind (D), Seeker ©, Warden (D): Although they use weapons, a lot of their powers (like telepathy, returning weapons, and fire damage) seem a bit beyond what non-arcane people tend to do. You may be able to work around those.
Assassin (HS) (S): The Lying Darkness is rumored to have had shadow-using ninja, but even if this was true, the Scorpion claim to have rooted out all such.
Barbarian (PHII) (S): Even wilder than the berserker, which means common only in the foreign-influenced Unicorn and the Tainted
Druid (PHII) ©, Druid (Protector) ©, Druid (Sentinel) (L) : As these include a few elemental powers, they could show different traditions of earth-spirit worship brought by the Unicorn and mixed with Rokugani shugenja spirit-talking (although apparently uncorruptible by shadow powers).
Monk (S): This is a good representation (and the best-known example in the setting) of the fancier things that non-arcane warriors can do. The multiclassing system doesn’t work well for those samurai who retire into it (although you could represent a character who has already done so and still has some other talents), but many of the Brotherhood of Shinsei are nobles or commoners who make it a lifelong way, and some noble families of the Dragon are made up of fire-breathing tattooed monks rather than swordsmen.
Vampire (S): That’s taking blood magic to a whole new level, which is not likely to be viewed positively even by the Crab.

DIVINE
There are no clergy of individual deities in Rokugani cultureā€”unless you count the worshippers of Fu Leng, who use shadow powers. The leaders in worship of the Fortunes and elemental spirits are shugenja, and the chief followers of Shinsei are monks.

Classes

Shiki Archlords