PC-based keyboard layouts for Mac OSX with some customizations. Thanks to Ukulele.

Copy to your ~/Library/Keyboard Layouts folder, and then activate them via System Preferences - Keyboard - Keyboard (tab) - Input Sources.

For less talk, just install, and fire up Keyboard Viewer from the menu bar (need to activate the viewer first it in System Preferences - Keyboard - Keyboard (tab) - Show Keyboard & Character viewers...).

For a longer read, go to http://blog.andreineculau.com/2008/12/30/custom_keyboard_layouts_with_romanian_diacritics#content (albeit that page has information about the outdated sibling keyboard layouts for PC).