Research Associate for LC???

Hello, gurus:

I have a very naive question here: I am going to be a postdoc at a medical school (biomedical research) with the job title "Research Associate". Is it possible for me to apply RIR (and the further Perm) through this? I know I need to have a permanent job offer letter, does that have to come from HR? Or a letter from the Dean's office will work?

Many many thanks