Th-Th-Th-threadjack!!
I've been thinking lately of focusing my road net more on hills (and resources) and less on diamond-grid "prettiness," and even experimenting with it a bit.
The other nice thing about roading hills is that the main unit moving around inside your empire most of the time is the lowly worker, which, with its two moves, is hit harder by unroaded hills and forests than most combat units are (since most of them are 1-move). Forests you can chop, hills you can't.
My thinking is, see what grid I get after counting roads for non-riverside resources, hills, and city-squares, then fill in from there. My experiments so far are rather inconclusive, but it's definitely not hands-down less efficient than the theoretically-ideal pretty diamonds everywhere, and it may be more so.