It's hard to say exactly, but if you can work through all the problems in Barber's Bayesian Reasoning and Machine Learning, and some other standard 'frequentist' stats text, you'd be well placed to get started.

My profile says where I work.

A lot of statistics. It's core.

It's unfortunate that biological statisticians have hijacked the term 'computational biology'. There's still a lot of computer science to be done in the area, particularly in genome assembly what with new sequencing technologies appearing every few years.

Certainly new algorithms and data structures are going to be crucial (e.g. Bowtie), but statistical analysis/scoring, even in a heuristic way, is always going to be an essential component just from the nature of the work being mostly about evaluating hypotheses from evidence.

I should have added data structures and algorithms to my list. De-novo assembly, alignment, phylogeny, and pretty much all sequence work rely heavily on advances in maths and comp sci.