I'm kinda stuck as a perma-DM, but the two characters I made that stood out were

Ragnar, the dwarven knowledge cleric. Here, I knew I needed to be a cleric since the group I was joining had just lost theirs. The rest was basically setting the "loves books" dials to maximum while finding a reason to work with everybody.

The second was <???> (I've forgotten the name), a half-orc fighter. Never got high enough for a sub-class, but this one was because the party needed a front-liner. I had his race, class, and background (folk hero). Personality inspiration hit when I rolled for height/weight and got 5'4" (short) and 190 lbs (heavy). He was sensitive about his height and hated to be mistaken for a dwarf. Enough so that he shaved his head and beard and emphasized his tusks. Blunt and honest.

So basically I've tended to go party niche --> personality, not the other way around. I made a few others, including one where I rolled everything. Ended up with a naive human death cleric. More comfortable around the dead (or undead) than around the living, she felt herself to be a psychopomp. Guide those whose time had come to the grave, keep those whose time it isn't yet out of the grave.