Ranjit,
The only time I got "Role does not exist" messages was when we tried to import a role but had not yet done a full sync, or if we tried to import the derived child role without importing the Parent role first.
This may sound silly, but be sure that the Parent role technical name in your import file is not messed up with a typo or space.
Have you searched through all the Notes on role imports? SP10 is rather behind the times, going on 4 years old now. SAP does recommend implementing support packs at least annually. I'd get more current if I were you.
Gretchen