When contemplating materials for any project, I always first assess what I have on hand and use it if possible. I feel that this is an historically accurate way to think about vernacular projects. "Making do" is an art form that has been preserved in many pieces that we've seen, including workbenches. We've come across some pretty funky workholding devices lately, whether looking over Jonathan Fisher creations, digging through the Old Sturbridge Village collection, or flipping through Woodworking in Estonia. It is wonderful to see natural crooks, bent knobby knees, or giant hewn slabs incorporated organically into useful and (yes) beautiful forms.
We have a pile of tree-length firewood at home that is currently sitting under several feet of snow, but before it became entombed in lustrous wintry cement I cut a 5' length of 12"-diameter ash and split it in half with wedges. I had in mind a shaving horse or some such project for it, but I think it'll be particularly suited for a Roman bench because it has quite a bit of mass. I envision using this bench to hew and carve, and ash should take this abuse reasonably well.
For legs, I turned to our resident beavers to do some work for me. I have nothing personally against beavers, until they attempt to flood the woods around our kids' treehouse or take down our nicest oak and yellow birch trees. These rodents (North America's largest) can do an unbelievable amount of work in a single night, and we've started incorporating beaver-processed materials into projects around the house. And why not? Trees are cut, peeled, and often forgotten in the woods to season. A handrail in our house, for example, is a polished beaver stick. We've seen many stake-leg workbenches that use rounds for legs, either as original construction or as later replacements (some still with the bark attached). Having a near-endless supply of downed saplings made this an easy choice - I simply dug out a good dry maple of the desired diameter (3" or so). Besides, how many people can say that a large rodent helped them with stock prep?
To read more about the first day of our Roman bench build check out this last post.