User defined roles on Linux

[S, Senthilprabu (NSN - IN/Bangalore)]

Hello All, 
    I am a newbie to Linux and SELinux as well. So apologize me if my question is stupid. All these days, I have been playing with Solaris. Have implemented user profiles and associated them with roles using RBAC on Solaris to facilitate set of users to run my application. Users assuming my role can only start, stop and troubleshoot application whereas not possible to execute any other commands. Now after RHEL 5.5 migration, I am trying to implement similar roles here too. After running through various RHEL manuals I assume that SELinux can be used to define RBAC roles to some extend, even though its main feature is to implement Mandatory Access Control (MAC). I see few pre-defined roles like  sysadm_r and staff_u. Now my question is it possible to create user defined roles on RHEL 5.5 using SELinux and assign it to shared os accounts?. If possible but not through SELinux, please let me how it can be done?.



Thanks in advance,
Senthil Prabu.S