What is rolloff in an op-amp circuit?

op-amp rolloff is an inherent low pass filter built into op-amp chips. Because op-amps have such a high gain, they are prone to breaking into high-frequency oscillation; therefore limiting the gain by frequency with a built in low pass filter helps stop this from happening.

Imagine a super small signal is leaking into an op amp, because of the high gain it becomes no longer negligible and we have a high frequency signal when the output should be zero. The low pass filter lowers the gain at these High frequencies.

Now, this will naturally create gain limits when designing circuits, forcing an upper bandwidth. This is adjusted for by lowering the gain you design into your circuit for the bandwidth you are dealing with (which is one of many reasons we build multi-stage amplifiers)