"Retour" is used figuratively to describe in the dialogue between two persons that in response to a certain verbal stimulus a speaker says something in their turn, usually something related to what was said to them; the word is sometimes found in the figurative expression "retour cinglant". As seen in this particular example below, this "return" can be realized several years after the words that prompted it were pronounced.
(ref.) Et, alors qu'il a qualifié Mitterrand d'« homme du passé », il doit encaisser ce retour cinglant : « Il est fâcheux qu'entretemps vous soyez devenu l'homme ...
(ref.) Le jour j, à Giscard qui l’avait qualifié en 1974 d’ "homme du passé", ciblant sa longue carrière dans les ministères de la IVème République, François Mitterrand joue sur les mots pour mieux dénoncer l’immobilisme du septennat écoulé. "Vous avez tendance à reprendre le refrain d’il y a sept ans, ‘l’homme du passé’, c’est quand même ennuyeux que vous soyez devenu dans l’intervalle, vous, l’homme du passif. Cela gêne un peu votre démonstration d’aujourd’hui".
"Faire une réflexion" means to say something of a particular sort to someone, something that is not pleasing to hear, something that is sufficiently critical to offend them.
(TLFi) Faire des réflexions à qqn. Faire des remarques désobligeantes.
It follows that there is no context of reply involved in the the concept "faire une/des réflexion(s)" and that the comments are always unkind, which is not the case in the figurative use of "retour" as it applies to dialogue.
In conclusion, it cannot be said that the two forms are synonymous, although "un retour" as applied to verbal exchanges can have something of the nature of a "réflexion" (unkind, of a nature to make someone feel guilty).
Do not confuse "faire une/des réflexion(s)" and "réflexion sur soi-même ou sur sa conduite" in the sense of thinking about oneself or one's behaviour ; those are totally different things.