
Apart from her contract with the MET, Ponselle offered recitals all along the US (and made a solid profit singing them), and also participated often in radio broadcasts.
Of course, she sung a few operatic arias in those events, but most of her repertoire were popular songs, other well known pieces and even some lied.
We can listen to Ponselle below in this other vein:
Ave Maria - Schubert
Der Erlkönig - Schubert
Träume - Wagner
Morgen - Strauss
O del mio amato ben - Donaudy
O sole mio - di Capua
So in love - Cole Porter

Ponselle promised to her mother that one day she would sing in Italy. In fact, she entered in negotations with La Scala in several occasions, but the great soprano, always a little bit insecure before a performance, had a insuperable terror to the Italian public.
Finally, she decided to accept in 1933 an offer from Florence's Maggio Musicale to sing there La Vestale, by Spontini, that was in her repertoire since 1925. Ponselle was happy about her command of the role of Giulia ("This is a pure singing role, there are no quick shortcuts or cheap dramatic tricks"), and thought this was a less risky piece for her first opera in Italy than works from Verdi, Giordano or Ponchielli.
In fact, the performances were a great success, and Ponselle received an enthusiastic ovation after singing "O nume tutelar". Mussolini himself requested to be introduced to the American singer, and asked her to visit Italy more often in the future. One performance was broacasted, with Dolci, Pasero and Stignani sharing the stage with Ponselle.
However, Rosa Ponselle never performed again in Italy.
Ponselle - O nume tutelar
Ponselle - Tu che invoco

The opera Ponselle was determined to sing at the MET in 1936 was no other than Adriana Lecouvreur. Maestro Serafin (that declared one day "In my lifetime, there have been three vocal miracles: Caruso, Ruffo and Ponselle") had introduced the role to her, and she was in love with Adriana, both from a singing and a dramatic point of view.
However, MET management was adamant they won't allow her to perform Adriana. This was one of the major reasons for Ponselle's retirement, and in retrospective it looks weird. The role was indeed ideal for the voice of the soprano, at that time of her career.
We can hear Ponselle, in the Villa Pace recordings, singing Adriana:
Ponselle - Poveri Fiori
Ponselle - Io son l'umile ancella