Open iPhoto. Select all photos with Cmd-A. Drag them to a folder. The end!
To preserve separate "rolls": open finder. Navigate to Photos. Right-click your iPhoto Library and choose "show package contents". Find the Originals folder and drag it out. You're set.
To preserve separate "rolls": open finder. Navigate to Photos. Right-click your iPhoto Library and choose "show package contents". Find the Originals folder and drag it out. You're set.