Patch meshes are great for detailed rocks and boulders, but beware of using too many cause that'll take the R_speeds through the roof.
What I do to create nice looking and r_speed friendly rocks is to make a block about 256x256x256 or what ever using the caulk texture, then on the forward pointing face apply your wanted rock texture. Then select the box, put it into place then either tweak the vertices (press V) or the edges (press E) to get the shape you want.
Using this method you have realistic rocks on the front and on the back side where the player can't see its nice and flat so the rocks fit together well.
I hope that helps