To answer the question you asked right here: yes. (But many do not, and neither are these "roots" exclusively christian. So what?)
In the same way, to answer the question in the thread title: no. "Western secular morals" - if such exists as one block - is derived from a lot of things, and by far not all of the christian. The "definition" of secular morals isn't derived from Christianity at all.
And again the counterquestion: so what?
Most "western" languages are derived from / have their roots in Latin or Old German. What should that mean for those who speak these languages?