Technically the law that governs this is determined on a federal level. The "one party of a recorded call is aware of the recording" is generally the current rule. There are 11 states that require both parties to be aware of the call recording. This does not apply, however, to an employer recording their employee's conversations as there is a provision within this law that permits any calls, including personal calls, to be monitored and recorded for general business use. The states that require two-party notifcation are:
California
Connecticut
Delaware
Florida
Massachusetts
Maryland
Michigan
Montana
New Hampshire
Pennsylvania
Washington
You need to be aware that the call recording will use voicemail ports, not VCM's, so be sure to have enough resources for all call recording and general voicemail use. I would also recommend not using mandatory recording as it will prevent calls from taking place if the voicemail is not available to record. Other than that, you turn it on and thank your own boss for not being so intrusive on your life.