The Roth 401(k) is a type of retirement savings plan. It was authorized by the United States Congress under the Internal Revenue Code, section 402A, and represents a unique combination of features of the Roth IRA and a traditional 401(k) plan. Employees can roll their Roth 401(k) contributions over to a Roth IRA account upon termination of employment. 2  It is the employer's decision whether to provide access to the Roth 401(k) in addition to the traditional 401(k).