This week's development video blog talks about how roles will be deployed during Early Enrollment and into Open Enrollment. Lee and Stephen use the term "class" and "role" pretty interchangeably in this interview, but they are just using "designer shorthand" rather than indicating a change in plans.
Remember that in Pathfinder Online, unlike the tabletop Pathfinder RPG, your character gains new abilities through the following basic process: They gain XP in realtime, as long as you have designated the character to receive XP (you might have multiple characters in one account, and not paid for more than one character at a time to gain XP, so you pick which character gets the XP.) You trade in XP at a trainer. Trainers require your character to have enough XP, and potentially to meet other prerequisites, and if all conditions are met, the trainer gives the character a new skill or a new level of an existing skill based on your choice. Character abilities are earned when a character meets all the prerequisites for a new ability, which almost always includes having a skill at a certain rank, and usually also requires the character to have reached an in-game achievement (and sometimes more than one!) or have fulfilled other prerequisites such as improving an ability score to a certain minimum threshold. Once these conditions are met, the character gains a new ability.
Character abilities may be associated with a "role", which is an analog to the tabletop "class" system, or they may not have a role association. You are free to mix and match the abilities your character earns, guided by the skills you are investing XP to train. Some players will focus their characters very strictly to progress along a "role" as quickly as they can. Others will want a more broad-based character and will gain a wider variety of new abilities. The advantage of the former strategy is becoming very effective in a narrow specialty quickly. The advantage to the latter is having the ability to do a wide variety of things even if the character isn't a master of any of them.
OK, enough with the lengthy system description, and on with the video!