Hi bscofield6, these fibulas worked almost the same way as the modern safety pins. They were used to fasten clothes (buttons were unknown for this purpose); besides that they had a decorative function.
@bubbas: you can rely on me: I detect for more than 25 years now and have found many, many roman fibulas. This brooch is a German one, normally found in Northern Germany. Compare it to this one, which I found some weeks ago http://forum.treasurenet.com/index.php/topic,43910.msg313075.html#msg313075
Reference book: O. Gupte, The knee-shaped fibulas (Bonn 2005)