The app offers a free voicemail service. When you turn on the voicemail in Settings, all messages will be sent to your email as MP3. Now you won't miss a single call.
Once you turn on "Receive calls when abroad", Roamer will ask you to enter your email and enable Voicemail. You can record your personal voicemail greeting to let your friends, family or colleagues know that you're currently on the road and will return the call at your earliest convenience.