Citations are usually exported between RIS, various bibliography formats from TEX/BibTex, Endnote formats or even XML. You need to use a dedicated bibliographic or text referencing software like the Reference Manager from Thomson Reuters.
Convert Research Information Systems citation to TeX/LaTeX text document.
We found one software available in the database for this conversion.
Microsoft Windows software - convert ris to tex on Windows
Bibliographic reference and citation management software
Convert from ris file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.