Yes, It's absolutely possible. Both of those functions have source code. It was possible for them to be written in the first place. It is possible for someone willing to figure things out to write similar functionality too.

Show what you've tried and where you're stuck so we can help you past the blockers.

Update: One thing I like to do is to establish in my mind (or on paper) what the rules are. Once you have a firm understanding of the rules for converting to Roman numerals, the rest is just a matter of putting them to code. The same goes for conversions to other bases; understand first how someone would do it without a computer, in 8th grade (give or take a year), and then put that to practice with code.