I’ve heard that in 1991 former Lell engineer went on to form a new company called Rostex. At least that’s the rumor and i have no other information about the brand or the pedal. You know anything about these (or have a demo clip/video), please do post it in the comment section.
For the layout, in addition to adding series polarity protection and input pulldown, i subbed the output buffer FET to common 2N7000 pinout.
4-knob version:
And the 3-knobbed version:
(Edit 25.5.2018 23:31: fixed a fault with low wiring and added the 3-knob layout
Edit 29.5.2018 20:35: Fixed 3-knob layout that had a misplaced cut on board image)