I use premade campaign settings, and roll almost everything else. Sometimes, I take stuff from video games.
For the next three months in game, the PCs will be defending a hidden dwarf mining colony between Nethra and Teth. There's also going to be an extradimensional dungeon that should resemble ancient India.
Sometimes, the rolls are a little strange. I used the table from the 3.5 DMG.
>Adp 5, Adp 2 (2), Adp 1, Ari 1 (2), Brb 2, Brb 1 (2), Brd 1, Clr 5, Clr 3, Clr 1 (2), Com 15, Com 7 (2), Com 3(4), Com1 (78), Exp 7, Exp 3 (2), Exp 1 (2), Myrmidion (Ftr) 6, Ftr 3(2), Ftr 1 (4), Stalker 2, Stalker 1 (2), Tortured Crusader (Pal) 4, Warpriest 2 (2), Warpriest 1 (4), Rgr 4, Rgr 2 (2), Rgr1 (4), Contemplative (Wilder) 3, Contemplative (Wilder) 1 (2), War 4, War 2 (2), War 1 (4).
>The highest level fighter is the sheriff, Dorgal Blackbanner. The religious authority is a faenor (priestess of Berronar Truesilver) with the healing and protection domains, since the previous priest of Dumathoin was eaten by a merrow.
>50 high level locals
>78 1st level commoners
>4 1st level warriors
>2 1st level experts
I don't know how a Dwarf Commoner made it to level 15 in Faerun, but I'm going to go with it.