How can physicists help in theoretical biology, besides math and fresh perspectives? By googling this keyword: "theoretical biology" and physics, I get many interesting pages, such as:


Physics meets biology: Bridging the culture gap
Biology is more theoretical than physics
Why physicists like models, and why biologists should
Biology is the new physics (note that this article's title is somewhat misleading in my opinion)


All pages I found mostly (or only, if I remember correctly) focus on the advantages of the physicists are their math background and being a neophyte so sometimes able to bring fresh perspectives to a problem. But that means a mathematician is also adequate to this.

My undergraduate dissertation is about biophysics, so I actually know that there are things that a physicist can help in biology. But mostly I see them in molecular biology. What else can physicists actually help with given their background?
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...