Elevator

Jobs represent the contract and the constraints to an individuals work; positions are the visibility and command and control and individual has through agency; and roles bundle the work into related groups of tasks.

Concerns

While these may be aligned and essentially have the same meaning it is not unusual for them to deviate from each other.  There is nothing wrong with deviation as long as the three remain related to each other.

Guidance

Implementation models like RACI (Responsibilities, Accountabilities, Consulted, and Informed) can be used to better understand how these three relate. Other variables include autonomy, authority, and accountability that an individual has.  Autonomy may be at the role level for an individual to accomplish a group of related tasks, however they may be responsible [work being done] rather than accountable [the finished deliverable] for the work, who still managed the overall work.  If an individual belongs to a formal profession, for example, they are usually both accountable and responsible.  In the case of the professional, though, they need the authority over the work to be accountable.