Rolling Active Pharmaceutical Ingredient and Drug Reserve Act or the RAPID Reserve Act This bill requires the Department of Health and Human Services to contract with drug manufacturers to ensure adequate supplies of critical drugs that have vulnerable supply chains. (Under the bill, drugs are considered critical if they are likely to be needed during a public health emergency or if a shortage would pose a significant threat to the health care system or at-risk populations.) Contracted drug manufacturers must agree to (1) maintain at least a 6-month reserve of the active ingredient in a critical drug and of the finished product and to regularly replenish these reserves, (2) produce the ingredient and drug in a manner and quantity as specified in the contract, and (3) agree to transfer portions of the reserve, if necessary, to other manufacturers to meet manufacturing needs and allow HHS to control the allocation of reserves in the event of a public health emergency or other threat. HHS must publish a list of critical drugs and issue guidance on the criteria for determining this list and awarding contracts. HHS must give preference to domestic manufacturers for contracts. In addition, the Government Accountability Office must report on the capacity of domestic manufacturing with respect to critical drugs, including the ability to manufacture different dosage forms and drugs with various characteristics.