Hi,
I am not sure but I guess there is no such parameter.
If you must do it like that, a possible work around is that:
create new access types, each access type contains only one specify role.
create multiple contacts for different roles of a user.
For example, for user lxpbn, you may have different contacts such as lxpbn_adm, lxpbn_analyst, lxpbn_emp, etc.
Each contact associate with assess type which contains the specific role.
Then you can use different username to login as different role.
Regards,
Mark