When you're in the initial base building phase, it's rare for a base to grow to bigger than size 2. That being the case, a base cannot utilize more than two developed tiles. To improve more tiles than that per base uses former time that could be better used for other projects.
If I don't already have a square that yields 2 nuts and 1 mineral, I first create one if possible (farm on a rolling moist square). Next, again if possible, I find a flat square, build a road (one turn) and then plant a forest on that square. I then build roads leading to the next base site.
Using formers to build roads creates turn advantage (Colony pods take fewer turns to establish a new base).
For more discussion on roads, see the following link:
http://apolyton.net/forums/showthrea...threadid=95633
(Hate Roads - What are They Good For?)