Most roll film is constructed using CTA (Cellulous Triacetate) which has little curl memory. Some films are constructed using PET (polyester). PET has strong curl memory however it is difficult to initiate a tear with PET. This makes it ideal for high speed machine developing and automated printing as these machine handle hundreds of films splice together under tension. High speed photofinishing was the idea behind 126, 110 and the Advanced Photo System (APS).
Your best bet is to send the films off for process by a lab that handles theses films with a continuous film process.
If this is not practical, try soaking the film in a distilled water bath. Dry the film by hanging with a weight. All this must be done in total darkness. That will not be easy. If this fails to take out the curl, add a few drops of glycerin to the water bath.
Best of luck!