For example, the word that means to assign a price is "price," so I can say that I priced something. I can't find the word that means to assign a probability, so for example, what is the correct way to say "I probability-ized something?"
Though not a single word, you could use the phrase to set the odds (intransitive) or to set the odds of [something] (transitive).
An odds compiler (or trader) is a person employed by a bookmaker or betting exchange who sets the odds for events (such as sporting outcomes) for customers to place bets on.
EDIT: This is not a good answer...see @Edwin Ashworth's convincing comments below. Seems the best answer is "assign probabilities."