you'll need to be more specific. up until the late 80's derosa's basic lineup usually only consisted of a single road and a single track model with a few low volume specialty framesets sporadically & briefly cropping up like the aerodynamica's. the early bikes had no serial numbering and evolved slowly, varying in small incremental details such as braze-on fittings, decalling, logo enscriptions,bridges, fork crowns and bottom bracket shells,etc.

after about 87 when the company moved from a small workshop into larger facilities, the number and variety of models expanded rapidly.

mostly detailed pics work best to identify & date any particular derosa

there's a few catalogs here spanning from the mid/late 70's to the late 80's that you might want to look at-
http://www.bulgier.net/pics/bike/Catalogs/

here's another nice resource-
http://www.43bikes.com/derosa.html