I'm assuming you bought Fl0yd's mechanical rotary add-on kit for your 49-way. The meat of that kit is a rotary 12-position electric switch. Currently you can only interface those with a Druin's interface, or by connecting all of the contacts on the rotary switch as buttons and using Mame Analog+. The Analog+ method only supports a few games, whereas the Druin's method works with all the mechanical rotary games.
The Optipac interfaces Optical rotary controls, like a mouse, trackball, spinner, or 360 degree steering wheel. So it won't work for Fl0yd's kit.