Roll-off describes the desired shape of the personnel resource profile for a project showing how people are re-deployed as a project winds down: we want the profile to decline gradually enough for the people to be absorbed by other on-going projects, avoiding a lay-off situation.
When the “roll-off” is precipitous, we have to quickly find placement for relatively large numbers of people having related skills. When we DO find placement during precipitous decline, people often end up in jobs for which they are poorly suited – neither the people nor the company are well-served.
We often adjust resource profiles from their original BoE for no other reason than to manage the roll-off and ramp-up. This is one of the main reasons why BoE are not typically used for direct management of projects.