Should I include research info from different field?

[Gust]

As is, I am applying to CS grad school even though I studied math in undergrad and all my research is in math.

The question is, in my personal statement, how sensible is it to talk in depth about my math research? I realize that personal statements should be "research-dense", but I don't know how reasonable it is for me to include detail about research unrelated to my field of study. (My CS interests are far apart from my math research). 

[prospectivecsgrad]

Yes.  Any research experience is research experience which will help your application when it is viewed by the committee.  Maybe talk about how the previous research you did influenced your current interests?