About Roads:
I wish there was a way to do it, since mountain ranges are virtually useless right now. Maybe it could be made so if you're going to embark into a mountain, you'll be limited to just mules instead of a wagon, limiting the amount of supplies you can carry in exchange for being able to travel deep into a mountain range like a proper dwarf. I can't help but think that having 40+ Z-slices would be murder on the game though, unless you're just settling a mountaintop...
About Prospecting:
We're already given hints about what the soil and rock in a particular area might contain, though. Most minerals only occur in a specific kind of rock or rock-layer. We're told what rock and soil layers exist in a zone that's about to be settled before embarking. If you see peat and sedimentary rock, it's safe to assume you're going to dig into some coal and maybe some limonite or something, for example. If you study the mineral tables on the Dwarf Fortress wiki, you can get an idea as to what occurs where and what your chances of prosperity are.
That, or you can take the easy route and always settle on a named volcano. I've yet to settle on one that didn't have gemstones and native metals sticking out in the open in generous quantities.
Seriously though, if prospecting is added it should give only a very rough and equally unreliable assessment of the total worth of the land about to be settled, like a mildly educated guess. Personally, I could live without it.