Which wrinkle filler works best for building collagen?

This is a very interesting question.  Two of the products that you mention, Cosmoplast and Restylane do not induce collagen production at all.  Cosmoplast is collagen and Restylane is a substance called hyaluronic acid.  Both rely on the volume of the actual material to fill wrinkles/lines.  Radiesse, a different substance altogether, relies on both the volume of the material and the production of collagen in response to the material to exert its effect.  Probably the most effective "filler" for inducing collagen production is Sculptra.  Sculptra relies almost exclusively on the body's collagen production to cause a more global revolumization of the facial structure.  It is therefore thought of more as a volumizing agent rather than a wrinkle filler.