Even thought the user has assigned the responsibility it is not appearing in the home page. Some times this is caused because of setting null at the "end date" of user define screen or because of expiration.
Metalink says that wf_local_user_roles and wf_user_role_assignments tables are not being in sync, so running the request Workflow Directory Services User/Role Validation
it may solve the problem.
Another simple workaround that i found very convenient for me is the following:
1. Update the "end date" field to something that will make the account expired.
2. Update the "end date" field again to something that will make again the account live.