Adding SOW Worker Roles is the fifth step in the creation of an SOW.

Though a statement of work is used to define a project—scope, timeline, deliverables, etc.—many projects will require specific roles to be filled in order to achieve the defined results, such as project manager or architect or accountant. This fifth step, adding SOW Workers, is where you define the specific role(s) necessary for completing the project.
To be clear, you're not literally assigning specific workers to the SOW—Joe Worker, for instance, is not being selected to work on the project. Instead, you're defining the types of workers that will be needed; the roles that will need to be filled.
For instance, if a project requires a software implementation specialist, that role will be added to the SOW. However, if no specific worker roles are required for a services project, SOW workers do not be defined and this step can skipped.

Any roles added here are derived from the SOW Worker Role admin object, which must be created before the SOW and associated to a supplier. This admin object is used for reporting purposes and helps ensure the worker's rate is accurate.