The chocolate truffles that you buy in the store can be kept out at room temperature.
But if you make the chocolate truffles at home using fresh cream then it needs to be refrigerated to keep the truffles from spoiling because of the cream.
Keeping the truffles in the refrigerator also makes them last longer and stay fresher than keeping them out at room temperature.
Still if you plan to eat the homemade truffles within the same day then leaving them out of the refrigerator is okay but any leftover truffles should be refrigerated.