(I know Civ V is out, but I enjoy IV so much more :) )
I'm figuring out my strategies for Monarch difficulty, trying to get my economy streamlined, and trade routes have popped up their head as a somewhat significant number.
My old strategy was to build roads generally on critical resources only, that provided gold, happiness, copper, whatever, and leave the non-critical developments like cottages, mines, and farms without roads on them.
Is there something to gain from building roads on every worked tile in the city cross?