Interested that people are recommending making the room more humid. Surely that's just delaying the curling? Or are you trying to avoid a sort of helix?
Oh the original issue, all (five) of the rolls of film I've developed have done this to some extent.
No it doesn't just delay the curling. You see the film can have a certain amount of moisture trapped in the emulsion without still being in need of drying. In other words it feels dry, appears dry, and you can even store them in sleeves yet the film still has some moisture in it.
Think of your film as a sponge. That emulsion layer absorbs liquid and then when dried shrinks down a bit. Now for arguments sake lets imagine that you only need to suck 95% of the moisture out of your film before its safely considered dry and ready to be cut and stored in sleeves. Now you shoot a roll, develop it and hang your film to dry in a room with very little humidity. You wind up sucking more than 95% of the moisture out and at the same time your getting excessive curling. By adding a bit of moisture to the air you are now capable of drying to that 95% figure and by keeping a bit of moisture in the neg you retard any additional curl.
I am not talking about making it a hot house with steaming vents everywhere. I am talking about adding just a little bit of moisture to the air. I actually have a really nice humidifier / dehumidifier in my darkroom and after years of use I have found I get the best results at around 15%-20 humidity.
Remember that other things can cause curling too. Again using a heater or having excessively long wash times will definitely lead to more curling. As long as you use a weighted film clip, wash for the proper times and refrain from a heating device you should be ok. If you find your still having problems try a bit of humidity.