Rome is built using mighty Maven! This is why these instructions are so short:-)
If you don't want to build Rome we'd suggest you download a binary build:-)
See Version Control for access intructions and to browse the source from your browser.
Check out the tag version-0-1 for version 0.1. Else checkout the trunk for the development version.
See Installing Maven for details.
Maven automatically downloads dependencies of a project from an online repository.