The Tribunal of the Rota Romana or the Sacred Roman Rota is the highest appellate tribunal of the Latin Rite and several of the Eastern Catholic Churches and is the second highest ecclesiastical court constituted by the Holy See. The Catholic Church has a complete legal system, which is the oldest legal system still in use today. The court is named Rota (wheel) because the judges, called auditors, originally met in a round room to hear cases....
The Rota is the highest appeals court, but it is not the highest court. If the Rota issues an invalid judgment, the judgment can be vacated before the Apostolic Signatura, the highest court of the Roman Catholic Church outside of the Pope himself. However, the legal powers of the Rota, not the merits of the case, are on trial before the Signatura: all the Signatura does is grant the petitioner a new trial in the Rota if the Rota was found to have erred in procedure.
Thanks for that additional information. This was all new to me.