Sheldon Brown has a nice overview of De Rosa:
"One of the major vintage lightweight race bikes. Many consider the top three to be Masi, Cinelli, and DeRosa. Ugo DeRosa represents the next generation of master builders. His bikes from the late 60's and early 70's are very rare. Bikes from the late 50's to early 60's are so rare that a price estimate isn't even possible. Bikes from around 1970 feature prominent cut-outs in all the lugs, unlike the modern examples with few cutouts. Early models were true hand-worked masterpieces, while the present day bikes have lost much of that flavor. All DeRosa bikes, new or old, do ride wonderfully. The geometry works, and the bikes are very well balanced. By late 70's or early 80's some unexpected flaws became somewhat more regular - gaps in brazing, for instance, are more common than one would anticipate. It really doesn't matter - the bikes still ride great and look pretty awesome too!"

Here is a photo of mine before it was stolen: