Cyclocross - Help With Choosing A Frame

I am a roadie who is looking for a frame on which I can ride both trails and road.. where I live in Nor cal there are some great trail rides split up by miles of roads. I would call it medium technical mtn biking stuff with roots and steep sections and rocks split up by 20 and 30 miles of road. I am looking for a bike that I could ride easily on the road and could take the pounding of the trails. I am considering the rivendell rambouillet or perhaps a straight cross frame. ANY GUIDANCE is appreciated... also any thoughts on tire selection for this kind of use... note.. there is some kinda steep downhill on dirt. THANKS!

If you are looking for a good cyclo cross that can take a pounding, then I recommend the Surly FFF. This bike take a beating from me at every race. And I am 230lbs...

-- fabien

LeMond Poprad is good and any Steelman would be the ideal for you.
Tires- Kenda Kross Supreme are the biggest, knobbiest, gnarly tires I can think of. They are also good on-road too. Heavy tires but goof for your situation.

The type of riding you described is exactly what I do with my Jamis Coda.
http://www.kustomz.com/coda1.jpg

Thaw,
Although the cross bike would be a faster bike for the dirt roads and commutes to the trails, I'm not sure you should get a cross frame. Riding a cross bike is challanging on anything technical. You also are running a lot greater risk of damaging wheels with a road wheelset that is typically on cross bikes. It is easier to ride a mtn bike on the road than to ride a cross bike on real mtn bike trails. I agree with Kustomz. A lightweight setup on a mtn bike frame will be more versitile. You can even race a non uci cross race with a bike like that. Good luck. Have fun.
cb