I bought a new unopened package of mascarpone cheese yesterday and forgot to put it in the refrigerator overnight. Is it still good to use?
That depends on how it was packaged; check the label. If it does not say something like "refrigerate after opening" or give a shelf life, assume that it must be refrigerated at all times and discard.
Note that this advise is very conservative, and you will have to evaluate your own tolerance for risk.