It's been advised that lighter infestations are tolerable. If you have a light infestation with only a few leaf rolls, then these can be picked off and destroyed.
For heavy infestations where most leaves are rolled; these should not be picked off. By doing so, you may damage the plant more than the sawflies themselves.
Cultivating the soil that surrounds the infested plant may expose any overwintering larvae, and these can be thrown on an elevated surface and fed to the birds!
Attract natural garden predators into the garden by providing spots of cover. Wild patches and strips of native wildflower/ grass can provide cover for predatory insects. Climbing plants such as ivy is excellent habitat for small songbirds.
Likewise, bird tables and ponds are an excellent resource for attracting wildlife.