1. propertyCondition

There is a confusion between propertyCondition and fieldCondition. The most common is node title. Correct use

->propertyCondition('title', 'blah', 'CONTAINS')

2. fieldCondition

->fieldCondition('body', 'value', 'A', 'STARTS_WITH')
column. This is the column in the database that should be matched, with field name prefix removed. For body field, the database columns are: body_value, body_summary, body_format, and language. 'value', 'summary', 'format', and 'language' are the actual arguments you would use. Likewise an image field would use 'fid', 'alt', and 'title' as column names; an entity reference field would use 'target_id' and 'target_type' as column names.
- This is a real drupalism
Tip For other custom modules, checking the hook_field_schema() makes it easy to identity the column name
- For role reference , in rolereference.module , is rid

<?php
 // Implements hook_field_info().
function rolereference_field_schema($field) {
  $columns = array(
    'rid' => array(
      'type' => 'int',
      'unsigned' => TRUE,
      'not null' => FALSE,
    ),
  );
  return array(
    'columns' => $columns,
    'indexes' => array('rid' => array('rid')),
    'foreign keys' => array(
      'rid' => array(
        'table' => 'role',
        'columns' => array('rid' => 'rid'),
      ),
    ),
  );
}
?>

Implementation in EntityFieldQuery

->fieldCondition('field_ref_role', 'rid' , $rid ,'=')

3. Multi step conditions

Best approach, sample code via Querying to get a list of taxonomy terms or nodes using EntityFieldQuery

<?php
$query = new EntityFieldQuery();
  $entities = $query->entityCondition('entity_type', 'node')
    ->entityCondition('bundle', 'article')
    ->fieldCondition('field_ref_role', 'rid' , $rid ,'=')
    ->propertyOrderBy('created', $direction = 'DESC')
    ->range(0,1);
  if (in_array('power user', $user->roles)) {
    $entities->fieldCondition('field_dummy','value',$myvalue,'=');
  }
  $result = $entities->execute();
?>

Tag approach, doesn't work with field condition, via

<?php
function mymodule_superblock(){
    $query = new EntityFieldQuery();
        $result = $query
            ->entityCondition('entity_type', 'node')
            ->fieldCondition('field_categories', 'tid', array('12','13'), 'IN')
            ->propertyCondition('status', 1)
            ->addTag('random')
            ->range(0,5)
            ->execute();
}
function mymodule_query_random_alter($query){
    $query->orderRandom();
}
?>