There's no contemporary source that describes direct relations between Radhanites and vikings, but ibn Khordadbeh certaionly reports that they operated in the same geographic areas and you can be sure they interacted in some way.

See: https://www.academia.edu/4809945/Radanites for a description of the routes and operations of the Radhanites. The Wikipedia article is also instructive and well-sourced: http://en.wikipedia.org/wiki/Radhanite

I think Sefer ha-Dinim may include an account of Jewish merchants (not sure if they are expressly identified as Radhanites) trading with Rus' merchants in early 11th century Kiev.