The latest version of RootsMagic 18.104.22.168 fixed a crashing issue when using CrossOver to run RootsMagic on a Mac. You "might" still get a GDI+ error, but you will need to get that fix from CrossOver.
First, launch Crossover, and then go to your Configure>Manage Bottles menu. Highlight the RootsMagic 5 (or 6) bottle, and then click on Applications, and then the "install software" button. This will open up the install software menu with the "RootsMagic 5" bottle pre-selected. Now, go to the "Community Supported Applications" section and select the package called "Platform SDK Redistributable: GDI+". Click on "install". Crossover will now download and install this package, which will be very brief. That's it! RootsMagic should function, again. Note that if you have told Crossover not to update the Install Software menu in the past, you might not see that "Platform SDK Redistributable: GDI+" package in the "Community Supported Applications" section of the install software menu. If that's the case, close the Install Software menu, and then go to the following webpage: https://www.codeweavers.com/compatibility/browse/name/?app_id=8227 Click on the green button that says "Install Platform SDK Redistributable: GDI+ via CrossTie" and open the file in Crossover. This will open up Crossover's Install Software menu, and you'll then be prompted to "Select a bottle into which to install". Select your "RootsMagic 5 (or 6)" bottle from the list, and then click "install" to proceed. That's it! RootsMagic should function, again.