Retourner can be used with avoir or être in compound tenses depending on its meaning in French (Le Passé Composé)

Most verbs use either avoir or être as the auxiliary verb in Le Passé Composé (Indicatif) (or other compound tense)but retourner uses both, depending on its grammatical usage* and what it means in the sentence.
 
*Grammaphile's Corner : the technical grammatical distinction between these cases is actually whether the verb is used in a transitive or intransitive manner. 
- The transitive version (the version with a direct object) uses avoir.
- The intransitive version (lacking a direct object), uses être.

Using avoir or être with the verb RETOURNER in Le Passé Composé (Indicatif) in French

être + retourné [quelque part]
= to go back [somewhere]
= to return [somewhere]

Je suis retourné dans le village où je t'avais rencontré.I returned to the village where I had met you.

C'était tellement amusant qu'il y est retourné plus tard !It was such fun that he went back later!

Note that in each case where être is the auxilliary, the verb retourner is followed by a preposition (en, sur, dans, à etc.).  
So, in these cases retourner is usually about going back somewhereor returning somewhere.

See also Agreeing past participle with subject's gender and number with (+ être) verbs in the compound past in French (Le Passé Composé)

ATTENTION
Retourner means to go back / home whereas revenir means to come back.

 

avoir + retourné [quelque chose]
= to turn [something] upside down
= to turn [something] inside out
= to turn [something] back to front

J'ai retourné ce pull parce qu'il gratte.I turned this jumper inside out because it itches.

Il a retourné sa casquette pour faire cool.He turned his cap back to front to look cool.

Tu as retourné la poubelle pour trouver tes clés !You turned the bin upside down to find your keys!

When retourner is followed immediately by a noun (as opposed to a preposition), it uses avoir as the auxiliary, like most verbs.   
ATTENTION: 
Retourner never means to return (something) in the context of a shop for example.
In French, we use rapporter (to bring back) or échanger [quelque chose] instead:
Elle a rapporté cette jupe comme elle était trop petite.She returned this skirt as it was too small.
  
 
Here is the list of all "two-auxiliaryverbs in compound tenses:
 

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Examples and resources

Il a retourné sa casquette pour faire cool.He turned his cap back to front to look cool.
Je suis retourné dans le village où je t'avais rencontré.I returned to the village where I had met you.
J'ai retourné ce pull parce qu'il gratte.I turned this jumper inside out because it itches.
Elle a rapporté cette jupe comme elle était trop petite.She returned this skirt as it was too small.
Tu as retourné la poubelle pour trouver tes clés !You turned the bin upside down to find your keys!
C'était tellement amusant qu'il y est retourné plus tard !It was such fun that he went back later!
Let me take a look at that...