nice illustrations Kevin.
To help put in perspective, 'scooped mids' is pretty much the definition of the metal tone that started in the late 80s with metallica and a number of other bands. they would EQ out the midrange, and it would produce this hollow sounding distortion that kind of hit you in the chest and felt like it was lowering the air pressure in the room or something. Very cool effect until everyone in the world seemed to be doing it and it became blasse.
Some people scoop the mids out of some things like kick to make room for the tracks that typically live more in that range, like guitars and vocals and keys. This is a matter of taste and opinion.
The "roll off" can happen at eitehr end of the spectrum, a low end roll off is usually used for tracks that don;t need a lot of that frequency, like guitars- generally rolling off soemof the low frequency stuff on guitars removes some of the muddiness you can get, and that low end is usually replaced with kick and bass. You might roll off the high end on the bass and kick for the same reason as well.
there is also high pass and low pass, high pass will let everything higher than a specified frequecy through, but kill everyhting below it and vice versa. the only real difference here is that the roll offs tend to be more gradual.
Daav