We first briefly review Dwork's trace formula and Wan's decomposition theorems. As an application, we consider a family of Laurent polynomials which is a generalization of the Laurent polynomials appeared in Iwaniec's work, and determine $p$-adic valuations for all the roots of the $L$-functions associated to an Zariski open dense subset of the space of Laurent polynomials. For lower dimension cases, we represent the Zariski open subset explicitly by computing an explicit Hasse polynomial.