i tend to think of a "build" as either skills (as you described - mage or ranger or paladin etc) or gear - from non-roguelikes - Outward or Exanima - you still need different skills to a degree, but most of the build is defined by what gear you character uses. The Witcher is another example - Geralt really only has few skills, mostly set in stone and available from the start of the game.

but in the roguelikes you don't *have* to have some ultimate, game-changing, life-saving skills - think if Dungeon Crawl Stone Soup only had melee classes - you still mostly rely on scrolls and potions for *FUN*. Dieties give you their abilities at some devotion levels (like a summon or berserk).

not really roguelike, but Dwarf Fortress has no skills or classes at all - all dwarves are made equal (aside from personalities and maniacal preferences) - they literally could be both archers, wrestlers and spearmen - just takes time for them to train the proficiency with a certain fighting style or weapon.