A consultant is generally someone who tells you what to do rather than doing it for you. Just sharing a wealth of experience. They might conduct research and write reports, then it's up to you what to do with it.
I would like to know too. I learn alot about SEO...but still doesn't know what a professional SEO's role is. May be i should start doing some internship. Anyone one interested? i can do it for free if i have a chance to learn new stuff