A Professional Randomist is someone with a wide and random assortment of skills. So random and wide that it is hard to describe their special talents and skills or a particular thing that they are good at.
Samantha knows how to do so many thing that it's hard to describe what kind of skills she has. She must be a Professional Randomist.
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).