what is roll-off in milimeter wave and mathametic formula?

Hello,

what is roll off and what is the exact value from which we consider to calculate roll off?

i know that roll off is transition from stop band to pass band (or passband to stopband) is known as roll off but i want to know that what is the mathematics value (like in rise time take a 5% to 95% as a rise time)

Thank you

your question is not making much sense. it might be the translation into English. could you restate the question a different way?

Hello
here i upload image from the paper which is the response of a band pass filter for the frequency range of 1THz to 1500THz.
from this transmission vs frequency plot,how i can calculate the roll off

can u please help me?
thank you