[asp.net] Add User to Role ASP.NET Identity

Check this link: Assigning Roles to Users. You can add a step to your CreateUserWIzard control and choose the roles in that step.

<asp:CreateUserWizard ID="RegisterUserWithRoles" runat="server" 
    ContinueDestinationPageUrl="~/Default.aspx" LoginCreatedUser="False" 
    onactivestepchanged="RegisterUserWithRoles_ActiveStepChanged">
    <WizardSteps>
        <asp:CreateUserWizardStep ID="CreateUserWizardStep1" runat="server">
        </asp:CreateUserWizardStep>
        <asp:WizardStep ID="SpecifyRolesStep" runat="server" AllowReturn="False" 
            StepType="Step" Title="Specify Roles">
            <h3>Choose the role.</h3>
            <asp:CheckBoxList ID="RoleList" runat="server">
            </asp:CheckBoxList>
        </asp:WizardStep>
        <asp:CompleteWizardStep ID="CompleteWizardStep1" runat="server">
        </asp:CompleteWizardStep>
    </WizardSteps>
</asp:CreateUserWizard>

And in the code-behind you will have:

protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        // Reference the SpecifyRolesStep WizardStep 
        WizardStep SpecifyRolesStep = RegisterUserWithRoles.FindControl("SpecifyRolesStep") as WizardStep;

        // Reference the RoleList CheckBoxList 
        CheckBoxList RoleList = SpecifyRolesStep.FindControl("RoleList") as CheckBoxList;

        // Bind the set of roles to RoleList 
        RoleList.DataSource = Roles.GetAllRoles();
        RoleList.DataBind();
    } 
}
protected void RegisterUserWithRoles_ActiveStepChanged(object sender, EventArgs e)
{
    // Have we JUST reached the Complete step? 
    if (RegisterUserWithRoles.ActiveStep.Title == "Complete")
    {
        // Reference the SpecifyRolesStep WizardStep 
        WizardStep SpecifyRolesStep = RegisterUserWithRoles.FindControl("SpecifyRolesStep") as WizardStep;

        // Reference the RoleList CheckBoxList 
        CheckBoxList RoleList = SpecifyRolesStep.FindControl("RoleList") as CheckBoxList;

        // Add the checked roles to the just-added user 
        foreach (ListItem li in RoleList.Items)
        {
            if (li.Selected)
                Roles.AddUserToRole(RegisterUserWithRoles.UserName, li.Text);
        }
    }
}