Jamieson, Fausset and Brown on 2 Chronicles 35:13

13. they roasted the passover with fire according to the ordinance--(See Ex 12:7-9). This mode of preparation was prescribed by the law exclusively for the paschal lamb; the other offerings and thank offerings were cooked in pots, kettles, and pans (1Sa 2:14).

divided them speedily among the people--The haste was either owing to the multiplicity of the priests' business, or because the heat and flavor of the viands would have been otherwise diminished. Hence it appears that the meal consisted not of the paschal lambs alone, but of the meat of the thank offerings--for part of the flesh fell to the portion of the offerer, who, being in this instance, the king and the princes, were by them made over to the people, who were recommended to eat them the day they were offered, though not absolutely forbidden to do so on the next (Le 7:15-18).