Using Rootsmagic 18.104.22.168 (23 May 2016) for Mac (latest version available).
Edit person -> Media -> Add new media -> Image -> Disk opens the Finder file selection pop-up. I select a PNG file (697 KB in size) and click Open. I'm returned to the Media Album, but the image is not shown. I am speculating that the presence of certain characters (e.g., parenthesis, commas) or the long filename (145 characters including .png suffix) are causing an error.
This looks like two bugs:
1. Inability to accept a filename which is valid within MacOS (in this case OS X 10.11.5).
2. Inability to report an error to the user (which should clearly describe the issue and what the user should do about it).