What permssions/roles to be assigned to a database user who is in charge of jobs?

I want to assign permissions/roles to a login who is in charge of creating, maintaining, and executing jobs. The login is the dbo of a database on which the jobs to be created. The problem I have is how to handle the permission in msdb for that login.

Hi ghemant,
I have tried all 3 SQLAGENT roles. It seems that those roles won't give permission to select the msdb..sysjobs and other system tables in msdb. Before creating any jobs or job steps, I need to check whether the jobs/job steps exist or not by querying those system tables.
Thanks for any help,
Peter