How can physicists help in theoretical biology, besides math and fresh perspectives?
One important contribution of physics to many areas is that physics is the origin of much of our understanding of complex systems phenomena, including emergence, chaotic systems, network effects, and phase transitions. Many areas of biology are still trapped in a hyper-reductionist framework (e.g., is FOXP2 the gene for speech) rather than realizing that such questions are poorly framed. Many biologists are embracing systems thinking, but the tools of physics are still not very widely dispersed overall, and collaboration that brings together such expertise with biological expertise (non-biologists are often frightfully naive about many realities of biology) can be of great value.

There are many other possibilities too, but this is a very important category that I think may be a good start...