Control methods are similar to Japanese Beetles. Use powdered rotenone or pyrethrum-based insecticides to kill Chafers. A new Neem-based product is available that repels the chafers. Or, manually knock them off your roses into a jar filled with water and kill them. Again, be sure to follow the instructions and precautions listed on the containers.
Wrens are very tolerant of human activity and they relish sawfly larvae.
The birds may not provide 100 percent control, but they help tremendously, and add to the enjoyment of your garden through their wonderful songs.