Just posted the following today
I have been using the trial version of InCall Recorder which has worked on my rooted S3 along with the Record feature.
Have asked Dev about saving the recorded messages on the ext. SD card which is stated in the description of the program but I have not been able to find out how to do it. The ability to do this is both in the Trail and Paid version description......just email them today.
Could not record through the Line but did get it through Mic. It was a pain to use the Manual Start to do this but it worked and the paid version has the Auto feature.
When I learn how to get this Record feature to save to that ext SD card, I will buy the program.
Try the Trial and post your results.