satisfactory
碌 centers on the idea of being satisfactory or adequate, often used in negative contexts to mean something is not up to standard. The meaning is narrow and typically appears in the common phrase 碌な (ろくな) meaning 'decent' or 'proper'.
碌 combines 石 (stone) with 录, which likely contributes the sound. The exact historical development is uncertain, but the character is used phonetically to represent the idea of adequacy or mediocrity.
A stone (石) beside a recording (录) suggests something solid but unremarkable—just satisfactory, nothing special.
For ロク, imagine a rock (ロック) that is only satisfactory: rock -> ロク, and the stone (石) in the kanji reinforces the image.
satisfactory; decent; good; proper; respectable
(not) well; (not) properly; (not) enough; (not) sufficiently; (not) satisfactorily; (not) decently
satisfactory; decent; good; proper; worthy
senility; dotage; decrepitude
(not) well; (not) properly; (not) enough; (not) sufficiently