I have been struggling to make roads and town squares for a while using various different methods. Hand scribing cobble stones onto a thin layer of plaster on MDF looks great, but it is wildly time consuming. Textured card glued to MDF or wood also works, but looks a bit flat and a bit fake for my liking. The best method I have now settled on is a textured rolling pin from a company called Greenstuff World at www.greenstuffworld.com
They produce a big range of interesting things for the modeler. I picked up some of their textured rolling pins. I found the 28mm scale one of cobblestones which is about 25cm long works really well for 1/72 scale cobbled town squares and roads. The detail stands out better than the smaller roller means for 15mm scale. I decided that I wanted to just make larger cobbled squares and put them together to make a large town area. Then the buildings would stand on top of the town area and the cobbled roads would be formed in between the buildings. Using MDF i cut a roughly 25 x 25cm square and then rolled out DAS clay nice and thin to the same size with a bit of an overlap. You then carefully and firmly roll the textured rolling pin over the clay in one direction making an imprint. I left this to dry, glued it to the MDF and then trimmed the edges.
I gave it a base in a grey spray primer and then used some brown and black washes and a whole heap of dry brushing lighter shades of grey. Check them out. When I have made a few I will set up a town scene to show the effect.