Roll off rate vs filter order?
assuming it's a low-pass filter and assuming that the filter order equals the number of poles and there are no zeros in the s-domain transfer function, then the rolloff at the edge of the passband through the stopband is -20 dB/decade (or -6 dB/octave) multiplied by the order of the filter.
now Butterworth and Tchebychev Type 1 filters have no zeros.
Tchebychev Type 2 and Elliptical filters have zeros, so the ultimate rolloff is not there, the gain remains at the stopband level.