The Roon KB has a page:
https://kb.roonlabs.com/DSP_Engine:_Parametric_Equalizer
You can think of a parametric EQ as a graphic EQ with adjustable bandwidth sliders rather than fixed.
The best primer for the Roon PEQ, after reading the above KB page is to play with it. Start with one filter and pull it around with your finger or mouse. Alter the Q to see what it does. Try out the different filter types. You’ll soon get the hang of it.
To get the V shape you might try three filters in combination. A low shelf for bass, peak/dip for middle and high shelf for treble. Once you’ve got the shape you want, you can shift the whole thing down so it is mainly cutting, perhaps 1 or 2 dB of boost at most.
Turn on the limit indicator in Headroom Management and dial in negative dB in -1 decrements until limiting stops.