What it means
ろくに〇〇ない indicates that an action is not done properly, sufficiently, or to an adequate degree. It commonly describes an action that happens very little or falls short of what is needed, and it is normally used with a negative predicate. The expression can refer to frequency, amount, or adequacy rather than to the manner of the action alone.
Usage note
ろくに〇〇ない is strongly associated with negative predicates. Do not confuse it with an expression meaning that an action is performed clumsily; it usually emphasizes insufficiency or an inadequate amount.
How to use it
ろくにVerb (ます-stem)ません
最近、ろくに食べません。
Lately, eating has not been adequate.
ろくにVerb negative stemない
最近、ろくに食べない。
Lately, eating has not been adequate.