What is the role of "dr-" at the beginning of certain adverbs?

Answer 1

Assuming you mean auf ==> drauf / über ==> drüber, the "dr" is equivalent to "dar" (as in "there").

It uses the directional component "dar" to turn a preposition into an adverb. The same happens with the "r", as a short form of "her" (hither), in "rauf" and "runter" [her + auf = herauf (up here) / her + unter = herunter (down here)].

HTH

Armin