Department of Homeland Security Reserve Service Act This bill amends the Homeland Security Act of 2002 to authorize the Department of Homeland Security (DHS) to establish a Homeland Security Reserve Service in each covered component of DHS, which shall provide for the temporary employment of former employees or the reemployment of annuitants of such component to stand ready to mobilize during elevated demands for, or critical shortages of, personnel and in times of crisis. DHS shall develop and implement an expedited process for hiring such employees and shall not use a competitive process. "Covered component" is defined as: U.S. Customs and Border Protection, U.S. Immigration and Customs Enforcement, the Transportation Security Administration, the U.S. Secret Service, or the Federal Protective Service of the National Protection and Programs Directorate. An individual who is employed or reemployed may be employed on a full-time or part-time basis, not to exceed one year for each assignment for which the individual is called into service. Not more than 1,000 individuals may be employed in the reserve service at any given time, to be divided across the covered components. DHS may waive this limitation for up to 90 days. DHS must implement the requirements of this bill within 180 days after its enactment and must certify to Congress that each covered component has a sufficient number of reserve personnel.