The problem is that RootkitRevealer doesn't actually identify rootkits. What it does is look for suspicious registry entries that may belong to a rootkit.
According to the SecuROM website, "SecuROM™ will install a Windows™ service module called “User Access Service” (UAService) on your system. This is a standard interface commonly used by several other applications as well. It is no spyware or rootkit at all. This module has been developed to enable users without Windows™ administrator rights the ability to access all SecuROM™ features. Please be assured that this service is installed only for security and convenience purposes. Since it is a standard Windows™ service, you can stop and delete this service, like any other Windows™ service. If deleted, the access for non-administrator users to SecuROM™ protected applications will be affected.
In other words, SecuROM is still a way for software producers to screw with you, but as of right now it's not a rootkit, and given recent public relations nightmares involving rootkits it's not likely to become one in the near future.
Source: Ars Technica