There's some variation in the following so YMMV, but: "Rolloff" tends--at least somewhat--to imply a relatively gentle decrease in response above or below a given frequency. "Filtering," on the other hand, tends to imply a possibly stronger action. By the time you get into steep filtering--12 or 18 dB/octave or even greater--that would almost certainly be called filtering rather than a rolloff.
With filtering, it's reasonable to want to know the turnover frequency (i.e. the -3 dB point on the curve) and the steepness in dB/octave (or alternatively, the number of "poles"); that way you can make much more meaningful comparisons. For example my Grace Lunatec V3 preamp has a switch setting for two-pole (i.e. 12 dB/octave) filtering below 50 Hz; "below 50 Hz" specifically means that the filter creates a -3 dB gain (or 3 dB of loss, if you prefer) at 50 Hz. With a rolloff, "below 50 Hz" wouldn't necessarily imply that the response is down 3 dB at 50 Hz although again, it might, especially if a specific slope is given (such as 6 dB/octave).
I hope that doesn't make things seem even more vague.
--best regards
P.S.: I don't get why someone would make the blanket statement that it's better to roll off in the microphone than in the recorder, except in cases of near-overload to the input of the recorder/preamp/mixer. In that case, sure, because the decreased voltages coming out of the microphone would be less likely to cause input overload in the preamp. That makes sense especially where wind noise is concerned. But otherwise, how often are you right on that threshold, and wouldn't there usually be a better solution available?