$user_data = get_userdata( $user_id );
if ( ! empty( $user_data->roles ) ) {
    if ( in_array( 'role_a', $user_data->roles, true ) {
        // custom content for role a
    } elseif ( in_array( 'role_b', $user_data->roles, true ) {
        // custom content for role b
    }
}