Steamroller is one of the earlier maps and was not included with 2.8.3 was reintroduced later. Cannot be found at aamission depot as it was offered through DCDS and included in later versions.
It is part of the mappack that was offered from AAops but since it became part of Battletracker it is no longer offered.
If you need maps such as these google them, that's how I found this one, took me like 30 secs to find it :P
google search ... mapname.aao
If you cannot find.. hit up one of our members that do have it, including myself, they can be uploaded (fileshare), made into a torrent (utorrent, bittorrent), or sent as a file transfer (TS3, xfire, MSN, Teamviewer)