I've spotted that this is a 3 year old post Kev (2006), but for your info:
Roughcast/dry dashing is where loose stone chippings are thrown onto a wet coat of mortar, that has been applied to a wall.
Wet dash is a like a wet concrete mix,, (using small chippings). This "wet mixture" is then thrown onto the wall. The wall is scratch coated first a day or two earlier,, then on the day of dashing, a thin coat of mortar is spread onto the scratch coat, and then the wet dash mix is thrown, "expertly" onto the wall.
Finished cement render should never be rough. Most render would be sponge finished (sandy texture), although it can be trowel finished (smooth). A "dry trowel" is VERY LIGHTLY passed over the surface of the render, in the final stages, just before the render has set.
Roughcaster.