Stating them up, 5e-wise, I'd do something a little funky like this:
Sturm: Cavalier Fighter, Knight of Solamnia
Tanis: Battlemaster Fighter, Custom BG: Observant feat
Caramon: Champion Fighter (or Brute, if UA's allowed), Mercenary Veteran
Raistlin: Lunar Sorcerer, Mage of High Sorcery (could also be a pact of the tome Undying warlock with Fistan as a patron and all ''eyes'' invocations).
Goldmoon: Redemption Paladin, Tribe member
Riverwind: Scout Rogue, Outlander
Tika: Thief Rogue, Custom BG: Tavern Brawler feat
Tass: Mastermind Rogue, Far Traveler
Flint: Berserker Barbarian, Clan Crafter
I think it keeps the low magic feel of the adventurers, making Raist the only main caster.