Roles managemant and sellect from DropDownList problem

Hi
I am using predefined membership and roles managemant approach
characteristic for framework 2.0

Basic idea is that we select some value from DropDownList which
represents a role and we get all users for selected role.
This works and that is not a problem.

Problem is in DropDownList control...

I am using select value as follow:
string roles = DropDownList_Roles.SelectedValue;

Recieived items
---------------------------------------------------------------------------
DropDownList_Roles.DataSource = Roles.GetAllRoles();
DropDownList_Roles.DataBind();

For e.g. if I get following vales:
ABC
AAA
CCC
RRR
FFF

What is wrong?
-----------------------------
Whatever I select, I always getting first value, in this case value
ABC.

Thanks for help.

Mike
.